Outboard Engines This sneak preview of your study material has been prepared in advance of the book's actual online release.

Transcription

1 Study Unit Outboard Engines This sneak preview of your study material has been prepared in advance of the book's actual online release.

2 iii Preview An outboard engine is a special type of small engine that s used to drive a boat. Many small-engine repair technicians never work on outboard engines. However, if you live in an area where water sports and fishing are common recreational activities, you may be called on to repair outboard engines. You may even decide to specialize in the repair of outboard engines. While it s true that you may or may not work on outboard engines, it s always useful to have additional skills that you can use in your business. And, since outboard engines are very similar to the small engines you ve already learned about, it won t be difficult for you to learn the few additional skills you ll need to repair outboard engines. This study unit will cover the components of the outboard engine, the basic operation of outboard engines, and how to troubleshoot, maintain, and repair these engines. When you complete this study unit, you ll be able to Identify the main components of an outboard engine List the parts found in the powerhead, midsection, and lower unit of an outboard engine Explain the basic operating principles of outboard engines Understand the special requirements of outboard engine fuel systems and cooling systems List the steps in an outboard engine tune-up Explain the procedures used to troubleshoot and repair outboard engine ignition systems, fuel systems, cooling systems, and drives

3 v Contents INTRODUCTION TO THE OUTBOARD ENGINE What Is an Outboard Engine? The Parts of a Boat The Parts of an Outboard Engine Outboard Engine Operation Outboard Engine Installation and Adjustment The Internal Components of an Outboard Engine THE POWERHEAD Outboard Engine Fuel Systems Outboard Engine Ignition Systems Outboard Engine Starting Systems THE MIDSECTION AND THE LOWER UNIT Outboard Engine Drives Outboard Engine Cooling Systems Propellers OUTBOARD ENGINE TUNE-UPS Performing a Compression Check Inspecting and Cleaning the Powerhead Adjusting and Checking the Ignition System Checking the Fuel System Synchronizing the Throttle Lubricating the Engine Performing a Tank Test Breaking In a New Outboard Engine Storing the Engine TROUBLESHOOTING OUTBOARD ENGINES General Troubleshooting Procedures Troubleshooting the Ignition System Troubleshooting the Electrical System Troubleshooting the Fuel System Troubleshooting Mechanical Problems in the Powerhead Troubleshooting Mechanical Problems in the Lower Unit POWER CHECK ANSWERS EXAMINATION

4 1 Outboard Engines INTRODUCTION TO THE OUTBOARD ENGINE What Is an Outboard Engine? An outboard engine is a special type of small engine that s used to drive a boat. Small outboard engines are used to drive small fishing and pleasure boats, while larger outboard engines are used on power boats. An outboard engine is mounted over the back of a boat with its propeller hanging down into the water. The engine is called an outboard because the entire engine is fastened on the outside of a boat. In contrast, an inboard engine is a larger, automotive-type engine that s mounted inside a boat. The propeller shaft of an inboard engine extends out through the body of the boat into the water. Inboard engines are typically used on very large, high-speed boats. We ll only discuss the operation and repair of outboard engines in this study unit. In some areas where water sports and fishing are common recreational activities, outdoor power equipment technicians will often be called on to repair outboard engines. Some technicians will even specialize in the repair of outboard engines. This type of business may be seasonal or yearround, depending on the climate. Also, depending on the type of shop you have and the type of work you specialize in, a customer may bring in an entire boat to be worked on; however, it s more common for the customer to remove the engine from the boat and bring it in for repairs. While it s true that you may not often work on outboard engines, it s always useful to have additional skills that you can use in your business. And, since outboard engines are very similar to the small engines you ve already learned about, it won t be difficult for you to learn the skills you ll need to repair outboard engines. Outboard engines are available in power ratings from 2 horsepower to 250 horsepower, and with one, two, four, or six cylinders. The engine cylinders may be positioned in an in-line (side-by-side) formation in the engine block, or in a V-type formation. The operating principles of most outboard engines are the same, no matter what their size or power output. Outboard engines are very similar in operation to other types of small engines the primary difference is the addition of the driveshaft and propeller that are used to drive the engine. Also, outboard engines are cooled by water, unlike the air-cooled small engines you ve studied in previous lessons.

5 2 Outboard Engines The Parts of a Boat At the present time, most of the outboard engines in common use are two-cycle engines. However, because oil and fuel are mixed together for use in two-cycle engines, these engines can allow pollutants to be released into the water during operation. To protect the environment, therefore, a movement is now under way to replace two-cycle outboard engines with four-cycle outboard engines. Soon, all brand-new outboard engines will be four-cycle engines. However, older two-cycle engines will continue to be used by their owners. Since outboard engines usually have long life spans and are typically used by their owners for many years, you ll no doubt be working on two-cycle outboards for a long time to come. Four-cycle outboard engines are very similar to the other four-cycle small engines you ve already studied, and the same methods are used to repair them. Therefore, we won t repeat all that information here. We ll primarily concentrate on the repair of two-cycle outboard engines in this study unit. Before we begin to discuss the construction and operation of outboard engines, let s take a moment to review some common boating terms. You ll need to be familiar with these terms in order to understand the servicing and maintenance instructions in manufacturers service manuals. Figure 1A displays a top view of a boat. Notice that the left side of the boat is called the port side of the boat. The left side of an outboard engine is called the port side of the engine. The right side of the boat and engine is called the starboard side. The front of a boat is called the bow, and the rear of the boat is called the stern. Figure 1B shows a side view of the same boat. The hull is the main body of the boat. An outboard engine is mounted on the rear of a boat in a section called the transom. At the base of the transom is an area called the keel. The Parts of an Outboard Engine Now that you know some basic boating terminology, let s look at the component parts of a typical outboard engine. Figure 2 shows the exterior of a typical outboard engine. Figure 2A shows a starboard view of the engine, and Figure 2B shows a port view of the engine. Take a moment to study the two views and familiarize yourself with the names of the exterior parts. This engine is a two-cylinder, water-cooled engine with a remote fuel tank. (That is, the fuel tank is separate from the engine, not built-in.) Inside the engine, the two cylinders are positioned horizontally. The two pistons are connected to a vertical crankshaft, and a driveshaft is splined to the end of the crankshaft. The driveshaft runs down the entire length of the engine and ends near the propeller. The lower end of the driveshaft is then splined to a right-angle drive gear assembly, and the drive gear assembly is connected to the horizontal propeller shaft.

6 Outboard Engines 3 FIGURE 1 The parts of a boat are labeled in this illustration. Figure 1A shows a top view of the boat, and Figure 1B shows a side view. FIGURE 2 The exterior parts of a typical outboard engine are shown here. Figure 2A shows a starboard-side view of the engine, and Figure 2B shows a port-side view. The propeller is connected to the end of the propeller shaft. When the engine is running, the turning motion of the crankshaft is transmitted through the driveshaft to the right-angle drive gear assembly, and from there to the propeller shaft and the propeller. When the propeller turns, the boat moves forward.

7 4 Outboard Engines An outboard engine is divided into three basic areas: the powerhead, the midsection, and the lower unit. The powerhead is the upper area of the engine that contains the flywheel, cylinder head, cylinders, pistons, connecting rods, crankshaft, crankcase, bearings, ignition system, and carburetor. If the engine is an electric start model, the powerhead will also contain the starter motor. The midsection of the engine includes the stern brackets, the exhaust housing, water-cooling passages, and the manual steering arm assembly. The lower unit at the bottom of the engine contains the engine s right-angle drive components, gearcase, propeller, and water pump. These areas are illustrated in Figure 3. Study the location of each component in the figure carefully. FIGURE 3 The locations of the powerhead, the midsection, and the lower unit are shown in this illustration. Note that some reference books and outboard engine service manuals don t use the term midsection. Instead, these manuals use the term lower unit to refer to both the midsection and lower unit components. This difference in terms isn t important as long as you know the names and functions of the separate engine components. The powerhead of an outboard engine is covered by an engine cover.on many engines, the engine cover is divided into a lower section and an upper section. The upper engine cover covers the entire top of the engine and helps to silence the engine. The upper engine cover also prevents the operator from coming in contact with the moving parts of the engine.

8 Outboard Engines 5 The lower engine cover is sandwiched between the upper engine cover and the exhaust housing. The lower engine cover often holds the steering handle, the starter handle (or the electric start switch), and the fuel line connector. In larger outboard engines, the remote control cables will pass through openings in the lower engine cover. Outboard Engine Operation Because the focus of this course is small engine repair, we won t go into a great deal of detail about boat operation here. However, in order to understand the repair of outboard engines, there are a few basic concepts that you should be familiar with. Let s take a moment to examine how an outboard engine is controlled by the operator. On smaller outboard engines, a manual steering handle is used to turn the engine and drive assembly. This action causes the boat to turn to the right and left. Larger engines, however, may be steered remotely. In a remote steering arrangement, an automotive-type steering wheel is used to drive the boat, and plastic-covered steel control cables connect the steering wheel to a linkage on the engine. A simplified illustration of a remote steering system is shown in Figure 4. FIGURE 4 A simplified view of a remote steering system is shown here. This type of steering system would be seen on a large, high-speed boat. Smaller outboard engines, such as those used on small fishing boats, are steered manually with steering handles.

9 6 Outboard Engines FIGURE 5 An exterior view of the parts of a remote speed control is shown here. On a smaller boat that s steered manually, the steering handle will also be used to control the boat s speed. The end of the steering handle is turned back and forth to change the engine s speed. On a larger boat that has remote steering, the speed will also be controlled remotely. A remote speed control will contain the ignition starter (a key or toggle switch) and a lever that s pulled back and forth to change the speed. The remote control is connected by cables to the ignition system and the engine s speed control linkage. Figure 5 shows the parts of a typical remote speed control. Outboard Engine Installation and Adjustment The proper installation and adjustment of an outboard engine are very important to engine performance and fuel economy. In addition, an improperly installed engine is a safety hazard. The first considerations when selecting or installing an outboard engine are the size of the engine, the engine s horsepower rating, and the horsepower rating of the boat. If an engine is too heavy and powerful for a boat, the boat may lift right out of the water and flip over at high speeds. The weight and power of an oversized engine will also place a great strain on the structure of a boat that s rated for a smaller, less powerful engine. A boat s identification plate will list its maximum horsepower rating. An engine is mounted to a boat s transom by its stern brackets. The stern brackets are held to the transom by one or two clamping screws. Figure 6 shows a closer view of the stern brackets mounted on a transom. The height of a boat s transom must be taken into consideration when selecting and installing the engine. An engine must be installed so that its propeller will be fully submerged at all times when the boat is running. This ensures that maximum thrust is obtained from the propeller. It also ensures that the water intake for the cooling system is fully submerged. An engine that s too long for a boat s transom height will produce excessive drag and reduce engine efficiency. Outboard engines are available in different driveshaft lengths to fit different boat transoms.

10 Outboard Engines 7 FIGURE 6 This illustration shows how an outboard engine is mounted onto a boat s transom. Some outboard engines also have adjustable stern brackets that allow the engine to be precisely positioned to obtain the best service. FIGURE 7 This illustration shows how the a boat s transom height affects the mounting of an outboard engine. Figure 7 illustrates how a boat s transom height relates to the mounting of the engine.

11 8 Outboard Engines An outboard engine must be properly adjusted on the boat in order to provide the best performance. One very important engine adjustment is the trim angle. The trim angle of an outboard engine is the angle at which an engine is tilted in toward (or outward from) a boat during operation (Figure 8). The adjustment of the trim angle has a very great effect on boat operation. The trim angle must be set correctly in order for a boat to operate safely and efficiently. When a boat operator adjusts an engine s trim angle in or out, he or she is said to be trimming the engine. In contrast, the tilt range of an engine is the distance that an engine can be tilted up out of the water. The engine will be tilted to its maximum distance out of the water when the boat is beached or loaded on a trailer. On smaller outboard engines, the trim angle can be adjusted manually by moving the adjustment rod at the stern brackets. A grip is provided in the engine cover that allows the engine to be tilted manually on a swivel mount. However, a larger engine may contain a power trim-and-tilt unit. This type of unit contains an electrically operated hydraulic pump that changes the engine s trim angle or tilts the engine out of the water. FIGURE 8 The trim angle of an outboard engine is the angle at which the engine is tilted toward or away from a boat. The trim angle must be set correctly in order for a boat to operate properly.

12 Outboard Engines 9 FIGURE 9 The trim angle of an outboard engine has a strong effect on boat operation. In Figure 9A, the engine s trim angle is set correctly, and the thrust developed by the propeller is parallel to the water surface. In Figure 9B, the engine is angled too far away from the boat, and the boat s bow rises too far up out of the water. In Figure 9C, the engine is angled too close to the boat, and the bow digs down into the water. The trim angle must be adjusted properly so that the boat will plane correctly. At a certain speed, a boat is said to plane when the bow rises higher than the stern, and the boat rides on the surface of the water rather than plowing through it. Figure 9 illustrates how adjusting the trim angle affects a boat s performance. When an engine s trim angle is set correctly, the thrust developed by the propeller is parallel to the water surface (Figure 9A). If the engine is angled too far away from the boat (Figure 9B), the boat s bow will rise too far up out of the water. If the engine is angled too close to the boat, the bow will dig down into the water (Figure 9C). Either of the incorrect adjustments will result in reduced engine efficiency, greater fuel consumption, reduced speed, and reduced maneuverability. In addition, if severe, these conditions could cause an accident. Note that a power trim-and-tilt unit should only be used to tilt the engine out of the water when the boat is being beached, launched, or loaded onto a trailer. Serious accidents and damage to the boat transom can result if the power tilt system is engaged while the boat is under way.

13 10 Outboard Engines The Internal Components of an Outboard Engine Now, let s take a closer look at the internal components of an outboard engine. Figure 10A shows a starboard-side view of a 4.5 horsepower outboard engine. Figure 10B shows a port-side view of a 7.5 horsepower outboard engine. The two engines are both two-cycle, water-cooled engines, with manual rope-rewind starters and manual steering handles. Both engines contain two cylinders. The 4.5 horsepower engine contains a built-in fuel tank, while the 7.5 horsepower engine gets its fuel supply from a remote fuel tank. The 4.5 horsepower engine weighs 51 pounds and has a piston displacement of 5.28 cubic inches. The 7.5 horsepower engine weighs 56 pounds and has a piston displacement of 10 cubic inches. Note that the upper engine covers have been removed from these engines. Both of these engines have the same basic structure. In each engine, the two cylinders are positioned horizontally. The two pistons are connected to a vertical crankshaft, and a driveshaft is splined to the end of the crankshaft. The lower end of the driveshaft is then splined to a rightangle drive gear assembly, and the drive gear assembly is then connected to the horizontal propeller shaft and the propeller. Note that both engines shown contain standard length driveshafts; however, engines with longer driveshafts are available for use in boats that have higher transoms. Take a moment to examine the engines in Figure 10, and note the positions of their various components. Then, look at the cutaway view of an outboard engine shown in Figure 11. In this figure, you can clearly see the positions of many of the internal components of an outboard engine. The engine shown in Figure 11 is a two-cylinder, manual-start 35 horsepower engine. The ignition system in this engine is a flywheel magneto type. Note the positions of the two spark plugs above the cylinders, and the location of the ignition module near the flywheel. At the very top of the drawing, you can see the flywheel. Note how the flywheel has teeth cut into its edge. A manually activated starter mechanism is positioned near the flywheel. When the starter rope is pulled, a nylon gear on the starter engages the teeth in the edge of the flywheel and starts the flywheel turning. Once the flywheel starts turning, it activates the engine s ignition system and gets the engine running. Although this engine is started manually with a pull rope, you should note that some outboard engines use lead-acid batteries and alternator-type charging systems to supply them with electrical power. The operation of this type of electrical system is the same as the system used in garden tractors. The 12-volt, lead-acid batteries used with outboard motors are much the same as the batteries used in garden tractors and automobiles. However, outboard batteries (often called marine batteries) are usually made with special waterproof cases that protect them from the elements during use. A special type of marine battery called a deep-cycle battery is used to operate special electrical equipment on boats, such as lights, fish finders, and bait tank pumps. However, deep-cycle batteries aren t always used for starting. Note the position of the two cylinders and pistons in the powerhead. The two cylinders are positioned horizontally next to each other, so this engine is said to have an in-line cylinder arrangement.

14 Outboard Engines 11 FIGURE 10 Figure 10A shows a 4.5 horsepower, two-cylinder outboard engine, and Figure 10B shows a 7.5 horsepower, two-cylinder engine. Note that the upper engine covers have been removed from both of these engines. (Courtesy of the Johnson Division of the Outboard Marine Corporation) The cylinders used in outboard engines are usually made of cast aluminum. An aluminum cylinder may contain a steel sleeve liner, or the cylinder walls may be specially coated with a protective material to prevent excessive wear of the soft aluminum. Steel-sleeved cylinders can be bored and refitted with oversized pistons during a rebuild. An aluminum cylinder with coated walls can t be bored it must either be replaced or refitted with a steel sleeve liner.

15 12 Outboard Engines FIGURE 11 In this cutaway view of a two-cylinder, 35 horsepower outboard engine, you can clearly see many of the internal components. (Courtesy of the Johnson Division of the Outboard Marine Corporation)

16 Outboard Engines 13 Next, look at the engine s crankshaft. The crankshaft is positioned vertically, and the driveshaft is splined to the end of the crankshaft. The other end of the driveshaft is splined to a pinion gear, and the pinion gear meshes with two gears on the propeller shaft. One of these gears controls the forward gear function, and the other controls the reverse function. Observe the position of the carburetor in the powerhead. This engine doesn t contain a built-in fuel tank instead, it uses a remote tank that s positioned inside the boat. A fuel line will connect the remote fuel tank directly to the carburetor in the engine. Note that some outboard engines may contain more than one carburetor. In the lower unit of this engine, you can see how the end of the drive-shaft is connected to a pinion gear. The pinion gear meshes with the two gears that are connected to the propeller shaft. These are the forward and the reverse gears. If the pinion gear meshes with the forward gear, the propeller will turn in the direction that moves the boat forward. If the pinion gear meshes with the reverse gear, the propeller will turn in the reverse direction and move the boat backward. THE POWERHEAD Now that you understand the basic position and operation of the parts of an outboard engine, let s take a closer look at the powerhead components. Remember that the powerhead is the upper area of the engine that contains the flywheel, cylinder head, cylinders, pistons, connecting rods, crankshaft, crankcase, bearings, ignition system, carburetor, and starter mechanism (or starter motor). An exploded view of a single-cylinder powerhead is shown in Figure 12. Note that the cylinder is positioned horizontally in this engine, and the crankshaft is mounted vertically. In this engine, the cylinder block is separated from the cylinder head by the head gasket. The crankcase holds the reed valve assemblies. When the crankcase and the engine block are bolted together, the bearings that hold the crankshaft in place are held firmly between the crankcase and the block. A seal is located at the outside surface of each crankcase bearing. These seals perform two functions: they prevent water, dirt, and dust from entering the bearing, and they also help maintain vacuum pressure within the crankcase. Note the shape of the crankshaft that s used in this engine, and observe the one-piece connecting rod. The connecting rod contains needle bearings in both ends. An exploded view of the components of a two-cylinder, in-line powerhead is shown in Figure 13. This is the powerhead of the 7.5 horsepower engine you saw earlier in Figure 10.

17 14 Outboard Engines FIGURE 12 An exploded view of the powerhead from a single-cylinder outboard engine is shown here. Note that the cylinder is positioned horizontally in the engine, while the crankshaft is mounted vertically. At this point, it s important to remember how two-cycle engines operate. In a two-cycle engine, the upward piston stroke is the intake/compression stroke, and the downward stroke is the power/exhaust stroke. When the piston moves up during engine operation, the piston creates a partial vacuum that draws the air-and-fuel mixture from the carburetor into the crankcase. When the piston moves down, the piston produces positive pressure that transfers the air-and-fuel mixture from the crankcase to the combustion chamber. Because of the way two-cycle engines operate, a multicylinder two-cycle engine needs a separate crankcase for each cylinder. Each crankcase must be of equal size and volume in order for the air-and-fuel mixture to be distributed evenly to each cylinder. The crankcases must also be isolated from each other to prevent leakage between them. The crankcases shown in Figure 13 are isolated by the center main crankshaft bearing and liner. The components of a two-cylinder, in-line crankshaft assembly are shown in Figure 14. This type of crankshaft is somewhat different from the single-cylinder crankshaft we looked at earlier. First, note that twopiece connecting rods with split bearing inserts are used with this crankshaft. Usually, a two-piece connecting rod will contain alignment marks on the rod and the end cap. When the end cap is attached to the rod, the marks should be aligned on the same side of the connecting rod.

18 Outboard Engines 15 A V-type powerhead is somewhat different in design than the in-line type. A V-type powerhead will usually contain a two-piece crankcase, but it may also contain an intake manifold between its cylinders. FIGURE 13 This illustration shows an exploded view of a two-cylinder, in-line outboard engine powerhead. (Courtesy of the Johnson Division of the Outboard Marine Corporation)

19 16 Outboard Engines FIGURE 14 Shown here is an exploded view of the crankshaft assembly for a two-cylinder engine. Outboard Engine Fuel Systems Two different types of fuel systems are used with outboard engines: the powerhead-mounted fuel system and the remote fuel system. In a powerhead-mounted system, a fuel tank is built into the engine s powerhead. A remote fuel system uses a fuel tank that s placed in the boat and connected to the outboard engine by hoses. Depending on the engine design, an outboard engine fuel system will contain the following principal components: A fuel tank A fuel pump or a gravity-feed system A fuel filter One or more carburetors A reed-valve assembly An intake manifold Most one-cylinder and two-cylinder outboard engines contain powerheadmounted fuel tanks. In most cases, a gravity-feed system is used to transport fuel from the tank to the carburetor. However, some engines have small, diaphragm-type fuel pumps built into their carburetors. Larger multicylinder engines will usually use portable, remote fuel tanks. Both types of fuel tanks are nonpressurized.

20 Outboard Engines 17 FIGURE 15 A remote fuel tank system for an outboard engine is shown here. Figure 15 is a simplified illustration of a typical remote fuel tank system. In a remote fuel tank, the fuel filler cap is provided with a vent that allows air to replace the fuel as it s consumed by the engine. The vents on most remote tanks are one-way valves that allow air to enter the tank but prevent fuel or fuel vapors from escaping. Some fuel tanks (especially auxiliary fuel tanks) use petcock-type air vents. A petcock vent can be opened or closed to prevent fumes from escaping or water from entering the tank. If the boat s operator forgets to open the petcock valve, the engine may stop due to lack of fuel. Outboard engines with remote fuel tanks usually use a diaphragm-type fuel pump to move fuel from the tank to the carburetor(s). A diaphragm pump will be mounted on the powerhead and operated by the pressure changes that occur in the crankcase. The operating principles of diaphragm pumps were discussed in the study unit on fuel systems.

21 18 Outboard Engines The Fuel In an outboard engine, gasoline with a minimum octane rating of 86 should be used. A marine engine lubricant should be used instead of automotive engine oils. Automotive oil will reduce the engine life as well as the spark plug life. In two-cycle outboard engines, the oil-and-fuel mixture should be 50:1 (fifty parts gasoline to one part lubricant). This is equal to six gallons of gasoline for every one pint of lubricant. Avoid using premixed fuel with an unknown quality lubricant. To fuel a small, two-cycle outboard engine with a powerhead-mounted fuel tank, premix the oil and fuel in a separate container, and then pour the mixture into the fuel tank. When filling portable tanks, gasoline should be added to the lubricant. Mix the fuel by tilting the tank onto its side, then back into an upright position a few times. When refueling non-portable remote fuel tanks, add the lubricant slowly through a large funnel as the tank is filled with gasoline. In cold weather, the required amount of lubricant should be premixed with about one gallon of gasoline. To refuel a portable fuel tank, add the remaining gasoline to this premix, then mix as described above. To fill a built-in remote fuel tank, add the premix slowly as the tank is filled with the remaining gasoline. Outboard Engine Carburetors Most one-cylinder, two-cylinder, and three-cylinder outboard engines use a single carburetor. The carburetor is usually a one-barrel, float-feed carburetor with a fixed high-speed jet and an adjustable low-speed jet. In some engines, however, the carburetor may have two fixed jets or two adjustable jets. In contrast, larger outboard engines often contain one or more two-barrel carburetors. Most two-barrel carburetors have two jets in each barrel a high-speed jet and a low-speed jet. However, some carburetors have three fixed jets per barrel a low-speed jet, an intermediate-speed jet, and a high-speed jet. The air-and-fuel mixture in most carburetors can be changed by replacing the air-bleed jet, the intermediate-speed jet, or the high-speed jet with a jet that has a larger or smaller inside diameter. Note that reducing the size of an intermediate-speed jet or a high-speed jet will produce a leaner mixture because it restricts the flow of fuel through the carburetor. However, reducing the size of the air-bleed jet restricts the flow of air and produces a richer mixture. Outboard Engine Ignition Systems Outboard engine ignition systems work in exactly the same way as other small engine ignition systems.

22 Outboard Engines 19 Outboard Engine Starting Systems The following two types of ignition systems are used most often in outboard engines: 1. The conventional flywheel magneto system with breaker point contacts operated by a crankshaft lobe 2. The flywheel magneto system with electronic ignition module (capacitor discharge type) Unlike some other types of outdoor power equipment, people tend to use outboard motors over very long periods of time. Since some of the engines you work on may be older, you should know how to service and repair breaker points. If necessary, refer to your earlier study unit on small engine ignition systems to review the operation of these systems and components. We ll discuss the repair and replacement of breaker points later in the study unit. Newer outboard engines will use electronic ignition modules to trigger ignition rather than breaker point contacts. Note that in outboard engines, the electronic ignition module is often called a pulse pack or a power pack. The power pack usually contains the capacitor, SCRs, diodes, and any other components needed to provide electronic triggering. The type of starting system that s used with an outboard engine depends largely on the size of the engine. Single-cylinder outboards and small multicylinder engines are usually equipped with manual starters. Many types of manual starters are available, and the type used with a particular outboard engine depends on the engine make and model. One type of rope-rewind manual starter is shown in Figure 16. This starter is used on the 7.5 horsepower engine that was shown earlier in Figure 10. When the starter handle is pulled, a nylon pinion gear slides up and engages the teeth in the flywheel edge. Once the engine starts, the pinion automatically disengages from the flywheel. FIGURE 16 A manual starter assembly is shown here. (Courtesy of the Johnson Division of the Outboard Marine Corporation)

23 20 Outboard Engines Larger outboard engines may use an automotive-type electrical system with a key switch, lead-acid battery, starter motor, solenoid, and alternatortype charging system. An outboard engine electric starter system will also typically contain a prevent-start switch that prevents the engine from starting unless the gear selector is set in neutral. The electrical system in a larger outboard engine may also include an electrically operated hydraulic pump to run a power trim-and-tilt system, plus the necessary wiring and controls for the pump. Figure 17 shows a simplified drawing of an outboard engine electrical system. Note the position of the battery in the figure. Also, note how a junction box is used to hold the electrical connections between the engine and the battery. The junction box is mounted in a protected location away from the fuel tank, the battery, and the floor of the boat (to protect it from water damage). FIGURE 17 This illustration shows a simplified view of an outboard engine electrical system. Note the position of the battery and the junction box in relation to the engine. THE MIDSECTION AND THE LOWER UNIT Now, let s take a closer look at the components of the midsection and the lower unit. Remember that the midsection of an outboard engine includes the stern brackets, the exhaust housing, the water cooling passages, and the manual steering arm (or steering linkage). An exploded view of a typical outboard engine midsection is shown in Figure 18.

24 Outboard Engines 21 FIGURE 18 This illustration is an exploded view of a typical outboard engine midsection. Division of the Outboard Marine Corporation) (Courtesy of the Johnson

25 22 Outboard Engines The main component of the midsection is the exhaust housing. The following are the components found in the exhaust housing: The exhaust relief hole The driveshaft The gear shift control rods The water pump The tube that delivers water to the powerhead The exhaust relief hole is used to relieve exhaust pressure when the engine is first started up, and also to discharge exhaust water during operation. Depending on the design of a particular engine model, the exhaust outlet may also be located in the exhaust housing. However, in the engine shown in Figure 11, the exhaust outlet is located in the propeller hub. In this engine, the main exhaust water moves through the passages in the exhaust housing, through the lower unit, and then out of the engine through the exhaust outlet. The exhaust housing is connected to the lower unit and helps to support it. For this reason, the exhaust housing can easily be damaged if the lower unit strikes a submerged object. The lower unit at the bottom of the engine contains the engine s rightangle drive components, gearcase, propeller, and water pump. An exploded view of a typical lower unit is shown in Figure 19. Study the location of each component in the figure carefully. The lower unit contains the following parts: The propeller The right-angle drive gear assembly The gear shift mechanism The water intake port for the cooling system The water pump Outboard Engine Drives The simplest type of outboard engine right-angle drive is the direct drive. Small, single-cylinder outboard engines generally use this type of drive. In a direct drive, a pinion gear is splined to the lower end of the driveshaft, and a matching bevel gear is splined to the end of the propeller shaft. The gears on the driveshaft and the propeller shaft are permanently engaged. When the engine is running, the propeller turns constantly and in only one direction. In order to reverse the direction of the boat, the engine must be pivoted 180 degrees on the swivel mount of the stern brackets. This pivoting will point the propeller toward the bow of the boat and cause the boat to drive in reverse.

26 Outboard Engines 23 FIGURE 19 In this exploded view of an outboard engine lower unit, you can see the components of the gearcase, the water pump, and the drive. (Courtesy of the Johnson Division of the Outboard Marine Corporation)

27 24 Outboard Engines Multicylinder outboard engines generally use a shift-type drive. The shift drive provides an outboard engine with the three functions of forward, neutral, and reverse. In this type of drive, a pinion gear is splined to the lower end of the driveshaft. Two bevel gears (a forward gear and a reverse gear) rotate freely around the propeller shaft. When the engine is running, the two gears rotate constantly, but in opposite directions. The engine shown in Figure 19 contains a shift-type drive. In the lower unit, you can see how the end of the driveshaft is connected to a pinion gear. The pinion gear meshes with the two gears that are connected to the propeller shaft. These are the forward and the reverse gears. If the pinion gear meshes with the forward gear, the propeller will turn in the direction that moves the boat forward. If the pinion gear meshes with the reverse gear, the propeller will turn in the reverse direction and move the boat backward. A device called a shifter clutch dog is splined to the propeller shaft. When the engine is in neutral, the clutch dog is centered between the forward gear and the reverse gear. To shift the engine into forward or reverse, the clutch dog is moved until it engages the desired gear. The clutch dog may be moved by a cam-and-plunger arrangement (as seen in Figure 19) or a yoke-and-fork mechanism (as seen earlier in Figure 11). If the clutch dog is moved to engage the forward gear, the propeller will turn in the forward direction. If the clutch dog is moved to engage the reverse gear, the propeller shaft will turn in the reverse direction. To prevent damage to the engagement surfaces of the clutch dog, the bevel gears, and the shifter mechanism, never shift an outboard engine into forward or reverse at excessive rpm. Also, shifting into neutral at high speed may cause the engine to over-rev. Outboard Engine Cooling Systems Most outboard engines are water-cooled. The powerhead of a water-cooled outboard engine contains channels through which water is circulated to cool the engine components. Water is drawn in through the water intake port, and is then pumped through the passages in the powerhead by the water pump (Figure 20). Circulation is controlled, in most cases, by a thermostat. (Some smaller engines, however, don t contain thermostats.) In the cutaway view of the engine shown earlier in Figure 11, note the location of the thermostat in the powerhead and the water pump in the lower unit. In many outboard engines, the water pump is located just above the gearcase, and is driven directly by the driveshaft. In some outboard engines, however, the water pump may be located in the gearcase, just in front of the propeller. Depending on the design of a particular engine model, the exhaust outlet may be located in the exhaust housing. Heated exhaust water moves through the passages in the exhaust housing, through the lower unit, and then out of the engine through the exhaust outlet. The exhaust outlet may be located in the exhaust housing or in the propeller hub.

28 Outboard Engines 25 FIGURE 20 The powerhead of a water-cooled outboard engine contains channels through which water is circulated to cool the engine components. Water is drawn in through the water intake port, and is then pumped through the passages in the powerhead by the water pump. Heated exhaust water will then exit the engine through the exhaust outlet. Depending on the engine design, the exhaust outlet may be located in the exhaust housing or in the propeller hub. (Courtesy of American Suzuki Motor Corporation) The water pump that s commonly used in the engines manufactured by Johnson and Evinrude outboard engines is the vari-volume type. The pump consists of two main components: a pump housing and a synthetic rubber impeller that contains several flexible blades. An exploded view of a typical water pump is shown in Figure 21. A top view of the impeller is shown in Figure 22. The impeller is fixed to the driveshaft with a pin. The pin fits into a slot in the impeller hub and rests against a flat spot on the driveshaft.

29 26 Outboard Engines FIGURE 21 An exploded view of a typical outboard engine water pump is shown here. This pump is driven by the vertical driveshaft. However, some pumps are mounted on the propeller shaft. The pump housing is offset from the center of the driveshaft. When the impeller rotates at low speed, the spaces between the impeller s flexible blades vary, as illustrated in Figure 22. The water pump intake port is located below the point where the impeller blades are farthest apart. The pump outlet is located above the point where the blades are closest together. When the engine operates at low speed, the pump functions as a displacement pump. Water is forced out of the pump outlet as the blades move closer together. Water is drawn into the pump as the blades move farther apart. When the engine operates at high speed, however, water resistance prevents the impeller blades from coming into contact with the wall of the pump housing. At high speeds, the pump functions as a centrifugal pump. The impeller blades are able to flex as a result of water resistance, which prevents water pressure in the cooling system from getting too high and possibly damaging the engine.

30 Outboard Engines 27 FIGURE 22 This figure shows a top view of a water pump impeller. (Courtesy of the Johnson Division of the Outboard Marine Corporation) Propellers FIGURE 23 The parts of a typical outboard engine propeller are shown here. The main function of the propeller is to provide the thrust that moves a boat forward. The shape and design of a propeller will have a great effect on the engine s performance. The propeller s blades are shaped rather like fan blades, and are mounted at a tilt on the propeller hub. When the propeller turns, the front of each blade pushes water forward, and the back of each blade pulls water with it as it turns. The parts of a typical propeller are shown in Figure 23.

31 28 Outboard Engines In the figure, note the different areas of the propeller blade. The blade face is the cupped side of the blade that pushes the water. The blade back is the side of the blade that pulls water behind it as the propeller turns. The leading edge is measured from the outer hub to the blade tip. The leading edge cuts into the water as the propeller turns, while the trailing edge follows behind. Now, look at the propeller hub. The outer hub is the area that comes into direct contact with water on the outside and exhaust gases on the inside. The blades are attached to the outer hub. The inner hub is a metal shell with a rubber interior. The inner hub may be splined or pinned to the propeller shaft. The inner hub is designed to absorb shocks if the propeller strikes a submerged object. The outer hub is connected to the metal surface of the inner hub by the ribs. This propeller uses three ribs to connect the inner and outer hub. The hollow areas between the inner and outer hubs are the exhaust outlets. Outboard engine propellers have two basic measurements: 1. Size 2. Pitch The size of a propeller is the diameter of the imaginary circle that can be drawn around the tips of the blades as the propeller spins. (An easy way to measure a propeller s size is to measure the distance from the blade tip to the center of the inner hub, and then multiply the measurement by 2.) The pitch of a propeller is the amount of twist that each blade has. The more angled or twisted the blades are, the higher the propeller s pitch will be. Figure 24 shows an illustration of propeller size and pitch. Propeller pitch and diameter have a strong effect on engine rpm at full throttle. A propeller that has a high pitch and a large diameter will have a lot of bite in the water as it spins. That is, the propeller will cut through the water easily and move a lot of water. A smaller propeller with a lower pitch will move less water. However, the large propeller requires more engine power to turn it against the resistance of the water. Less engine rpm is needed to run a small propeller. If a propeller s diameter is too small and its pitch is too high for operating conditions, the water resistance against the propeller will cause the engine to labor. On the other hand, if the propeller is too large and the pitch is too low for operating conditions, the water resistance will be reduced too much. This can cause the engine to overspeed, especially at full throttle. An outboard engine will be factory-equipped with a propeller that allows the engine to run at full throttle under average operating conditions. However, the design of the boat and different operating conditions may make it necessary to select and install a different propeller. For example, if a boat will be used to pull water-skiers, the drag on the boat will be increased greatly. To allow the engine to operate at full throttle while pulling skiers, the engine s original propeller should be replaced by a propeller with a lower pitch. Now, take a few moments to review what you ve learned by completing Power Check 1.

32 Outboard Engines 29 FIGURE 24 This figure illustrates the concepts of propeller size and pitch. At the end of each section of your Outboard Engines text, you ll be asked to check your understanding of what you ve just read by completing a Power Check. Writing the answers to these questions will help you review what you ve learned so far. Please complete Power Check 1 now. 1 5: Indicate whether each statement is True or False Power Check 1 In an outboard engine, gasoline with a minimum octane rating of 86 should be used, and automotive engine oil should be used for lubrication. A small propeller with a low pitch will require a lot of engine rpm to turn it against the resistance of the water, while a propeller with a high pitch and a large diameter will require less engine power to run. If an engine contains a shift-type drive, in order to reverse the direction of the boat, the engine must be pivoted 180 degrees on the swivel mount of the stern bracket. A power trim-and-tilt unit should only be used to tilt the engine out of the water when the boat is being beached, launched, or loaded onto a trailer. In a remote fuel system, a fuel tank is built into the engine s powerhead. (Continued)

33 30 Outboard Engines Power Check : Fill in the blanks in the statements. 6. An outboard engine is mounted on a boat s by its stern brackets. 7. The of an outboard engine is the angle at which an engine is tilted in toward (or outward from) a boat during operation. The of an engine is the distance that an engine can be tilted up out of the water. 8. Depending on the design of a particular outboard engine model, the exhaust outlet may be located in the or in the. 9. In an outboard engine that uses a direct drive, a pinion gear will be splined to the lower end of the driveshaft, and a matching bevel gear will be splined to the end of the. 10. In most water-cooled outboard engines, water circulation is controlled by a that s located in the engine s. 11. In many outboard engines, the water pump is located just above the and is driven directly by the. 12. A good way to measure a propeller s size is to measure the distance from the to the center of the, and then multiply the measurement by two. 13. The left side of a boat is called the side and the right side is called the side. 14. An outboard engine can be divided into three areas called the, the, and the. Check your answers with those on page 69. OUTBOARD ENGINE TUNE-UPS Tuning and adjusting an outboard engine is not unlike tuning and adjusting any other small, two-cycle engine. The procedures outlined in the following sections of your study unit are applicable to virtually any make or model of two-cycle outboard engine. The purpose of a tune-up is to maintain an engine at peak operating efficiency. A tune-up can also uncover mechanical problems that may be causing an engine to operate below peak efficiency. Before proceeding with a tune-up, however, you should first determine whether the engine has any special problems that may need attention. This information may be obtained by questioning the owner of the engine, or by test-running the engine, either on the boat or in a testing tank. (We ll discuss tanktesting a little later in this section of your study unit.) A simple visual inspection may also reveal problem areas. For example, blistered paint on the engine cover may indicate that the engine is overheating.

34 Outboard Engines 31 In a small engine repair shop that services outboard engines, a special mounting table or bench will be needed to hold the engine during a tuneup. All that s really needed is a solid, raised bench area that the engine s stern bracket can be clamped onto. Mount the engine on the bench in the same way it would be mounted on a boat. Make sure that the engine is securely fastened and that the bench can t tip over from the engine s weight. Be sure to follow all of the standard workshop precautions that were discussed earlier in the course when working on outboard engines (for example, disconnect the spark plug wires before beginning work, make sure the shop is adequately ventilated, and so on). Also, before conducting any performance tests, be sure to remove the propeller and replace it with a test wheel to prevent injury. (We ll discuss this in more detail in a moment.) A typical outboard engine tune-up will include the following: A compression check An inspection of the powerhead A check of the ignition system A check of the fuel system A throttle synchronization Lubrication of the engine A tank test Now, let s take a closer look at each of these tune-up procedures. Performing a Compression Check The first step in an engine tune-up procedure is perform a compression check. Before beginning the test, however, the ignition system should be disconnected to prevent the engine from starting accidentally. If an engine has an electronic ignition system, separate the connector plug between the magneto and the power pack. If an engine has a breaker points ignition system, disconnect the spark plug wires from the spark plugs and ground them. To perform the compression test, you simply turn the engine over by hand and gage the amount of compression in the cylinders. (If an engine uses an electric starter, turn the engine over by pulling the emergency starting rope.) There should be a lively bounce as each piston passes top dead center (TDC). In general, the compression is too low if the engine doesn t bounce well as each piston passes TDC, and is too high if it s particularly hard to pull past TDC. A slow cranking speed in an electric start engine isn t an accurate indication of compression. Slow cranking may be caused by either an undercharged battery or an excessive voltage drop in the starter system circuitry. Therefore, slow cranking can indicate either too much compression or too little compression.

35 32 Outboard Engines Some manufacturers recommend that a compression test be performed with a compression gage. To get the highest possible reading when performing this type of compression test, the engine should be cranked through at least four compression strokes with the throttle wide open. Whichever method is used, the compression in each cylinder should be checked. If you use a compression gage to perform the test, a difference of more than 10 psi between cylinders indicates a problem. Also, if the compression reading is between 10 psi and 15 psi less than the optimum compression specified in the manufacturer s service manual, a problem condition exists. If you observe any of these conditions during your test, you ll need to remove the cylinder head (or heads) and the exhaust cover to determine the cause of the problem. If the compression of one or more cylinders is too low, check the condition of the cylinder walls, pistons, and piston rings. If the compression is too high in one or more cylinders, the condition may be caused by an excessive buildup of carbon on the cylinder head or piston head. Inspect the exhaust ports, cylinder head, pistons, and piston rings. If you find excessive carbon deposits, the powerhead will need to be disassembled and cleaned. Inspecting and Cleaning the Powerhead Some outboard engine manufacturers recommend that the cylinder head and the exhaust cover be removed during a tune-up procedure. This will allow you to closely inspect the cylinder head, cylinder walls, pistons, piston rings, and exhaust ports for excessive wear or carbon accumulation. After you remove the cylinder head and the exhaust cover, rotate the flywheel slowly in a clockwise direction, and visually inspect the pistons, piston rings, and cylinder walls. The flywheel should turn smoothly and evenly. Note that you should never rotate the flywheel in a counterclockwise direction, since this may damage the blades of the water pump impeller. Next, check the pistons, piston rings, and cylinder walls for signs of excessive wear or damage. Check to see whether the piston rings are sticking as a result of excessive carbon accumulation. If any of these conditions are found, you ll need to remove, disassemble, and repair the powerhead. (We ll discuss this procedure in more detail in a moment.) If the pistons, piston rings, and cylinder walls appear to be in good condition, carefully scrape any carbon deposits from the exhaust ports, and clean any petroleum gum and varnish deposits off the pistons or rings with cleaning solvent. Carefully clean any carbon deposits from the top of each piston. If the deflector on the top of the piston is scored or marred, it will disrupt the flow of air-and fuel mixture into (and exhaust gases out of) the combustion chamber. When the parts are clean, reinstall the exhaust cover. Always use new gaskethoroughly clean any old gasket material or cement off the gasket surfaces. ts when reassembling powerhead components, and remember to Unless otherwise specified by the gasket manufacturer, lightly coat both sides of the gaskets with gasket sealing compound.

36 Outboard Engines 33 Before the cylinder head is reinstalled, it should be resurfaced to remove any high spots from the gasket face. Then, reinstall the cylinder head using a new gasket. Lightly coat the gasket on both sides with gasket sealing compound unless otherwise specified. The cylinder head bolts should then be tightened in the recommended sequence to the manufacturer s specified torque. Adjusting and Checking the Ignition System To check the ignition system, visually inspect all cables, wires, and connections for breaks, worn or broken insulation, pinched wires, dampness, oiliness, and tightness. Then, remove and replace the spark plugs. Be sure that the new plugs are the type recommended by the manufacturer, and make sure that the plug gaps are adjusted to the proper specification. Also, before installing the spark plugs, make sure that the spark plug seat is clean. To inspect, adjust, or replace the breaker points in an outboard engine, it will be necessary to remove the flywheel. Note that multicylinder engines will often contain a set of points for each cylinder. After removing the flywheel, visually inspect the breaker points for wear, burning, pitting, or other damage. Worn or damaged points should be replaced. If the points are in satisfactory condition, adjust them to the proper point gap specified in the service manual. Next, before replacing the flywheel, inspect the crankshaft and flywheel taper for oil traces. Excess oil in either of these areas may indicate that an upper crankshaft seal is leaking. After your inspection is complete, replace the flywheel. No check of an ignition system is complete until a spark test is performed. To test for spark, disconnect the spark plug wire from each plug, then connect a spark tester to the spark plug wire. Some spark testers allow two or more plug wires to be connected and tested at the same time. If your tester doesn t allow this type of test, disconnect and ground the other spark plug wires. Grounding the wires will prevent arcing or a damaging buildup of high voltage in the ignition system. Set the tester s air gap as specified in the manufacturer s service manual. For breaker-type ignition systems, the air gap is usually set at about 1 4 inch. When testing electronic ignition systems, the tester s air gap is set to about 1 2 inch. Checking the Fuel System During the tune-up procedure, the fuel system should be given a thorough visual inspection. The carburetor, fuel lines, fuel filter, and choke should be carefully inspected for leaks, cleanliness, and overall condition. The fuel filter element should be cleaned or replaced as necessary. If the engine is equipped with a fuel shut-off valve, it should also be checked. The carburetor adjustments should be performed during the tank test or after the engine is reattached to the boat.

37 34 Outboard Engines Synchronizing the Throttle To obtain the maximum performance and fuel economy from an engine, it s important to properly synchronize the throttle and the magneto. The throttle and magneto are linked so that as the throttle is opened, the spark automatically advances. The method used to synchronize the throttle and magneto varies depending on the make and model of engine. (Consult the engine service manual to determine the manufacturer s recommended procedure for a particular engine.) The following method would be used to synchronize the throttle and magneto of the 4.5 horsepower and 7.5 horsepower engines shown earlier in Figure 10. Advance the throttle until the marks on the throttle cam are centered on the cam follower, as shown in Figure 25. At this point, the throttle valve in the carburetor throat should just be opening. FIGURE 25 The location to make a throttle cam adjustment on an outboard engine is shown here. (Courtesy of the Johnson Division of the Outboard Marine Corporation) To adjust the throttle valve position, turn the cam follower adjustment screw out until the throttle valve is completely closed. Then, turn the screw in until the throttle valve shaft just begins to rotate. It s important to be sure that the marks on the cam are still centered on the cam follower. The throttle and magneto are now synchronized. In the previous step, it s often difficult to tell just when the throttle valve shaft starts to rotate. However, the simple, homemade tool shown in Figure 26 can help. The tool is made from an alligator clip and a piece of stiff wire. Clip the tool to the throttle shaft just opposite the cam follower. The tool will exaggerate the movement of the throttle shaft and make it easier to see when it starts to rotate.

38 Outboard Engines 35 FIGURE 26 Shown here is a homemade tool that you can use to assist in adjusting the throttle cam. (Courtesy of the Johnson Division of the Outboard Marine Corporation) Lubricating the Engine To obtain reliable service and to prolong the life of an outboard engine, it must be regularly lubricated according to the manufacturer s specifications. It s also important to use the right lubricants. Most outboard engine manufacturers recommend using lubricants that are especially designed for use on their products. The chart in Figure 27 lists the lubrication points on a typical outboard engine. The table also lists the type of lubricants that should be used, as well as a lubrication schedule. Note that engines that are used in salt water require more frequent lubrication than engines that are used in fresh water. This is because salt water is more corrosive than fresh water, and breaks down oil-based lubricants much more quickly. Figures 28A through 28E show the lubrication points on a typical outboard engine. When you re lubricating the gearcase, the ignition system should be disconnected to prevent accidental starting of the engine. If you suspect a leakage of lubricant from the gearcase, the gearcase should be pressuretested. To pressure-test the gearcase, remove the propeller and drain the gearcase. Install a gearcase pressure tester in the drain hole as shown in Figure 29. Pump air into the gearcase until the gage reads between 3 psi and 6 psi. Then, immerse the gearcase in water. If you observe bubbles escaping from the gearcase, the gearcase seals are faulty and must be replaced. (After the seals are replaced, pressure-test the gearcase again.) If no bubbles are seen, increase the pressure in the gearcase to between 16 psi and 18 psi. If there are still no bubbles, the gearcase seals are good. Remove the pressure tester and reinstall the drain plug. Finally, slowly refill the gearcase with lubricant to permit trapped air to escape (Figure 30).

39 36 Outboard Engines LUBRICATION POINT LUBRICANT FREQUENCY (PERIOD OF OPERATION) Clamp screws, steering handle, tilt/run lever FRESH WATER SALT WATER OMC Triple-Guard grease 60 days 30 days Fuel shutoff linkage, choke, throttle linkage Shift lever shaft, swivel bracket (upper and lower) Throttle cam, carburetor linkage Rear motor cover latch Gearcase (capacity 14.7 oz or 435 ml) OMC Triple-Guard grease OMC Triple-Guard grease OMC Triple-Guard grease OMC Triple-Guard grease OMC HI-VIS gearcase lube 60 days 30 days 60 days 30 days 60 days 30 days 60 days 30 days Change after first 20 hours of operation and check after 50 hours of operation. Add lubricant if necessary. Drain and refill every 100 hours of operation or once each season, whichever occurs first. FIGURE 27 This chart lists lubrication recommendations for the 4.5 horsepower and 7.5 horsepower engines that were shown earlier in Figure 10. (Courtesy of the Johnson Division of the Outboard Marine Corporation) Performing a Tank Test Whenever you test-run an outboard engine, it s very important to remember that an outboard engine should never be run out of the water. Without water resistance on the propeller, an outboard engine will overrev, so much so that it may be irreparably damaged. Also, a water-cooled engine will rapidly overheat if run out of water. This can result in severe (possible irreversible) damage to the powerhead. To test-run an outboard engine in a repair shop, a testing tank is used. A testing tank is simply a large tank filled with water. Most small engine repair shops that service outboard engines are equipped with test tanks. If your shop doesn t own a tank, you can use an oil drum filled with water to test small outboards. Again, an outboard engine should never be run, even momentarily, out of water. For this reason, if a test tank isn t available, the engine must be installed on a boat for the final test run. The tank test is usually the final stage of the tune-up procedure. During a tank test, an engine is mounted on the tank and allowed to run in the water. The purpose of the tank test is to Check and adjust the timing (if necessary) Adjust the carburetor jets Check the efficiency of the cooling system Evaluate overall engine performance

40 Outboard Engines 37 FIGURE 28 Figures 28A through 28E show the lubrication points on a typical outboard engine. Apply OMC Triple- Guard grease from a tube to the points marked with the number 1. Apply OMC Triple-Guard grease with a grease gun to the points marked with the number 2. (Courtesy of the Johnson Division of the Outboard Marine Corporation)

41 38 Outboard Engines FIGURE 29 A gearcase pressure tester is used to pressurize the lower unit and locate leaks. (Courtesy of the Johnson Division of the Outboard Marine Corporation) FIGURE 30 After pressuretesting a gearcase, slowly refill the gearcase with lubricant to permit trapped air to escape. (Courtesy of the Johnson Division of the Outboard Marine Corporation) Before beginning a tank test, all of the nuts, bolts, and screws on the engine should be tightened to the manufacturer s specified torque requirements. A sample torque chart from a manufacturer s service manual is shown in Figure 31. The propeller must also be removed from the engine and replaced with a test wheel for safety during the test. The test wheel can accurately simulate actual operating conditions during the tank test. Note that an outboard engine should never be run (even in water) without a propeller or a test wheel attached to it. The manufacturer s specification sheet will indicate the proper diameter and width of the test wheel that should be used on a particular engine. Figure 32 shows examples of the test wheel dimensions to be used with two different engine sizes. The best results will be obtained from the tank test, particularly with respect to carburetor adjustments, if a tachometer is used in conjunction with the test wheel. The tachometer permits more accurate rpm readings. After a tank test is completed, and after the engine has cooled until it s comfortable to the touch, the cylinder head bolts and spark plugs must be retightened to their specified torque values. When tightening the cylinder head bolts, remember to follow the manufacturer s recommended torquing sequence to prevent the cylinder head from warping.

42 Outboard Engines 39 Flywheel nut Connecting rod screws cylinder head screws Crankcase to cylinder head screws Spark plugs Pull at propeller shaft to tilt up lower unit Power pack mounting screws Ignition coil mounting screws TORQUE CHART POWERHEAD 4.5 hp Engine 7.5 hp Engine ft. lbs in. lbs in. lbs in. lbs ft. lbs lbs. 4-5 ft. lbs. 5-7 ft. lbs ft. lbs in. lbs ft. lbs in. lbs ft. lbs lbs. 4-5 ft. lbs. 5-7 ft. lbs. Warning: Failure to comply with recommended torque values could result in operator injury or motor damage. STANDARD SCREWS Inch-Pounds Foot-Pounds Newton-Meters No No No No When tightening two or more screws on the same part, DO NOT tighten screws completely, one at a time. To avoid distortion of the part, first tighten all screws together to one-third of specified torque, then to two-thirds of specified torque, then torque down completely. Re-check torque on cylinder head screws and spark plugs after motor has been run and has reached operating temperature, and has cooled comfortable to touch. FIGURE 31 The chart shown here lists the torque requirements for 4.5 and 7.5 horsepower outboard engines. (Courtesy of the Johnson Division of the Outboard Marine Corporation) Now, let s take a closer look at each of the checks and adjustments that are performed during a tank test. Adjusting the Ignition Timing Many small single-cylinder and two-cylinder outboard engines won t require ignition timing adjustments. However, the ignition timing of larger engines should be checked and adjusted with the aid of a timing light.

43 40 Outboard Engines FIGURE 32 A typical test wheel is shown here. An outboard engine s propeller is replaced with a test wheel during a tank test. (Courtesy of the Johnson Division of the Outboard Marine Corporation) The following procedure describes the steps used to check the ignition timing in the 35 horsepower, two-cylinder outboard engine you saw earlier in Figure 11. Note that the two cylinders of the engine are referred to as Cylinder 1 and Cylinder 2. Step 1: Disconnect the spark plug wire from the spark plug over Cylinder 1 and connect the timing light to the wire. Step 2: Step 3: Run the engine at full throttle. The timing mark should align with the 34 degree mark on the flywheel. A reading of plus one degree or minus one degree is generally acceptable. However, if the timing is off by more than one degree, it should be adjusted. To adjust the timing, stop the engine and turn the timing adjustment screws to either advance or retard the timing. Then, restart the engine and recheck the timing with the timing light. Note that the methods used to check and adjust the timing of larger engines may differ, although the basic principles are the same. Detailed instructions on how to adjust the timing will be provided in the manufacturer s service manual. Adjusting the Carburetor To properly adjust the carburetor on an outboard engine, the engine must be run until it reaches its normal operating temperature. The carburetors on most outboard engines have only one adjustable jet the low-speed jet. The high-speed jet is fixed and doesn t need adjustment. However, if the carburetor is equipped with an adjustable high-speed jet, it should be adjusted first. To make carburetor adjustments, run the engine at full throttle. Then, adjust the high-speed jet knob until the highest rpm reading and smoothest operation is obtained. However, allow the engine some time to respond to the adjustment (between 15 and 30 seconds is generally sufficient).

44 Outboard Engines 41 To adjust the low-speed jet, set the throttle so that the engine runs at 700 to 750 rpm. Then, adjust the low-speed jet knob until the highest rpm reading and smoothest operation is obtained. After adjusting the low-speed jet, you can readjust the high-speed jet, if necessary, by following the procedure described above. Performing a Temperature Check The effectiveness of an outboard engine s cooling system can be checked by testing the temperature of the powerhead. To test the powerhead temperature, special testing sticks are used. The testing sticks are similar in appearance to large crayons and are made of temperature-sensitive, waxlike compounds (Figure 33). The compounds are formulated to melt at specific temperatures. The normal operating temperature range of most outboard engines is between 125 F and 165 F. For this reason, two sticks are used to test a powerhead s temperature one that melts at approximately 125 F, and another that melts at approximately 165 F. FIGURE 33 The temperature of a powerhead can be checked with a testing stick as shown here. (Courtesy of the Johnson Division of the Outboard Marine Corporation) It s best to test the powerhead temperature while the engine is attached to a boat, since this type of test more accurately simulates the actual conditions under which the engine is operated. However, you can perform a temperature test in a test tank. The test procedure is simple. Run the engine for at least five minutes at about half throttle. When the engine is running at between 900 rpm and 1,000 rpm, make a mark on the cylinder head with both testing sticks. In their unmelted state, the wax marks will appear dull and chalky. Note that testing sticks will sometimes not make a mark on a painted surface. In such a case, you ll need to hold the sticks against the powerhead surface during the test. Continue to run the engine, and observe the wax marks. When the temperature of the powerhead surface reaches 125 F, the mark made by that stick will begin to melt and appear glossy. If the powerhead reaches a temperature of 165 F, the mark made by that stick will become glossy.

45 42 Outboard Engines If the 125 mark melts but the 165 mark doesn t, the engine is running within the proper temperature range. From this test result, it s also safe to assume that the cooling system is functioning properly. However, if the 165 mark melts during the test, the engine is running too hot. A number of different problems could cause this condition, such as a clogged water intake, a faulty thermostat or water pump, or a blockage in the powerhead cooling passages. (The troubleshooting of outboard engine cooling systems will be discussed later in the study unit.) On the other hand, if neither wax mark melts within a reasonable length of time, the engine is running too cold. Generally, this problem is caused by a faulty thermostat. To check the powerhead temperature of a smaller outboard engine that doesn t contain a thermostat, you ll use only the 165 testing stick. Hold the 165 stick against the side of the cylinder block (not against the cylinder head). The reading shouldn t be taken from the cylinder head, because the cylinder heads of smaller engines are generally hotter than the maximum operating temperature of the engine. You can then evaluate the results of the test as outlined above. Breaking In a New Outboard Engine When a new outboard engine is being broken in, the continuous use of full power must be avoided for the first five to ten hours of operation. Full-throttle operation should then be increased gradually to allow the moving parts to seat themselves. The following schedule of operation is recommended to break in a two-cylinder outboard engine with a power rating of up to 35 horsepower. First hour: Run the engine at low speed for a minimum of fifteen minutes. Thereafter, operate the engine at full throttle for periods of up to one and one-half minutes at intervals of five to ten minutes. Second hour: Increase the duration of full-throttle operation to between one and two minutes, then slow to half-throttle or three-quarter throttle to allow the engine to cool off. After second hour: Full-throttle operation may be increased after the second hour, but avoid continuous use of full power for extended periods of time for the next three hours. Consult the service manual for the engine to learn about any further operating restrictions. During the break-in period, check the operation of the cooling system periodically to ensure that it s working properly and that there s no danger of the engine overheating. To do this, check the overboard indicator located at the rear of the exhaust housing just below the powerhead. If the overboard indicator is discharging water, the cooling system is operating properly. Note, however, that not all engines are so equipped. Some engines, for example, contain temperature sensitive switches in their cylinder heads. If the engine temperature rises beyond the maximum, these switches will close and sound a warning horn in the control box.

46 Outboard Engines 43 Storing the Engine In most areas of North America, the climate only allows outboard engines to be used for part of the year. During the off-season, the engines must be stored. The storage period in some cases may be as long as ten months. However, before an outboard engine is stored for any length of time, steps must be taken to prevent deterioration. Particular attention must be paid to the cylinders, pistons, and cooling system. To prevent rust from forming on the pistons and cylinder walls, the cylinders should be protected with a coating of oil or rust-preventing compound. To do this, remove the spark plugs and pour a small quantity of engine oil into each cylinder. Then, turn the engine over by hand (pull the starter cord) a few times to distribute the oil. To protect the crankcase, crankshaft, carburetor, manifold, and leaf valves, outboard engines should also be fogged before being stored. In the fogging procedure, a rust-preventing oil compound is sprayed into the carburetor intake (or into specially provided fogging hole) while the engine is running. The fogging procedure is continued until the engine stalls or smokes excessively. The oil compound can also be sprayed into the cylinders through the spark plug holes to distribute the oil through the cylinders and around the pistons. If the outboard engine contains a built-in fuel tank, drain the fuel system. Then, check the fuel lines and the fuel filter, and clean them if necessary. If the engine uses a remote fuel tank, you can either empty the tank before storage, or treat the fuel with a stabilizer. This prevents the gasoline from breaking down and allows fuel to be stored in the tank for up to one year. Next, drain the cooling system. The cooling system should also be flushed out if the engine has been used in salt water or silty conditions. Drain and flush the lower unit, and refill the gearcase with the proper lubricant. Now, remove the propeller and grease the propeller shaft thoroughly. Then, lubricate the engine as described earlier in the text. Apply a coating of automotive wax to the exterior of the lower engine cover and the exhaust housing. Disconnect the spark plug wires to prevent an accidental engine start. Finally, place the engine in an upright position in a dry, well-ventilated area. When you remove the engine from storage to prepare it for use, thoroughly inspect the engine for worn or damaged parts, leaky gearcase seals, and loose screws. Start the engine up, then check the operation of the cooling system to make sure that the water pump hasn t seized. Finally, before returning the engine to regular service, perform a thorough engine tuneup according to the procedures described earlier. Now, take a few moments to review what you ve learned by completing Power Check 2.

47 44 Outboard Engines 1 4: Fill in the blanks in the statements. 1. When an outboard engine is tank-tested, the propeller must be removed and replaced by a. 2. The effectiveness of an outboard engine s cooling system can be checked by testing the temperature of the. 3. The normal operating temperature range of most outboard engines is between degrees F and degrees F. 4. After an outboard engine is tuned up, a final test run should be performed, either on a boat or in a. 5 14: Indicate whether each statement is True or False. Power Check 2 5. In order to inspect an outboard engine s cylinder head, cylinder walls, pistons, piston rings, and exhaust ports for excessive wear or carbon accumulation, you ll need to remove the cylinder head and the exhaust cover from the engine. 6. Engines that are used in salt water will require lubrication less often than engines that are used in fresh water. 7. If a water-cooled outboard engine is run out of the water, it will rapidly overheat, which could result in severe damage to the powerhead. 8. To inspect, adjust, or replace the breaker points in an outboard engine, it will be necessary to remove the flywheel. 9. An outboard engine should never be run (even in water) without a propeller or a test wheel attached to it. 10. New gaskets should always be used when a powerhead is reassembled. 11. Outboard engines require little or no preparation for long-term storage, except for draining the fuel from the fuel tank. 12. Outboard engine gearcases are factory sealed and don t require lubrication. 13. A compression check, a throttle synchronization, a lubrication of the engine, and a cleaning of the powerhead components are all recommended procedures when performing a complete tune-up of an outboard engine. 14. When a compression test is performed on an outboard engine, the compression in each cylinder should be checked. Check your answers with those on page 69.

48 Outboard Engines 45 TROUBLESHOOTING OUTBOARD ENGINES General Troubleshooting Procedures The procedures used to troubleshoot an outboard engine are the same as those used to troubleshoot any other small engine. Troubleshooting is essentially a process of elimination. The possible causes of a particular problem are systematically checked and eliminated until the fault is identified. Then, effective measures are taken to correct the identified problem. The most common engine problem is the no-start condition. As mentioned earlier in this course, three conditions must be met before an engine can run properly. First, the ignition system must produce a spark of the right intensity at the right time. Second, the proper amount of fuel must be mixed with the right amount of air, and this mixture must be efficiently delivered to the combustion chamber. Third, there must be sufficient compression in the cylinder so that the air-and-fuel mixture can burn to produce maximum power. If the engine fails to meet any of these conditions, it will fail to start (or at least, run poorly). The following are the most frequent causes of a no-start condition: No spark, weak spark, or improperly timed spark No fuel, insufficient fuel, or an improper air-and-fuel mixture Weak compression Therefore, when you re troubleshooting an outboard engine, your first task is to identify which of these three conditions isn t being met by the engine. You can determine the cause of the trouble by systematically testing the components of the ignition system, the electrical system, and the fuel system. You ll also need to check for mechanical failures in the engine. The procedures used to troubleshoot these engine systems have been discussed in earlier study units. However, we ll review some troubleshooting procedures here that apply particularly to two-cycle outboard engines. Troubleshooting the Ignition System There are two basic types of outboard engine ignition system problems. These are 1. No spark, weak spark, or intermittent spark 2. Improper spark timing If the ignition system fails to produce a spark, or if the spark is too weak to properly ignite the air-and-fuel mixture in the combustion chamber, a problem exists in one or more of the components of the ignition system. Improper timing, however, results from an improper adjustment of the throttle synchronization linkage or improper ignition timing. Throttle synchronization and ignition timing were discussed earlier in the section on engine tune-ups.

49 46 Outboard Engines As always, the first step when troubleshooting an ignition system is to give the system a complete visual inspection. Follow these steps to perform a visual check: Step 1: Step 2: Step 3: Step 4: Check the system for loose connections, broken or corroded wires, worn or damaged parts, damaged insulation, dampness, or oil-soaked wiring. Examine the spark plugs and replace them as necessary. Make sure that each plug is gapped to its correct specification. Inspect and clean the spark plug wires. Pay particular attention to the terminal connections at the plugs and the ignition coils. If the engine contains breaker points, remove the flywheel and examine the points and condenser(s). Check the condenser mounts and connections, and tighten them if necessary. Check the breaker point gap and compare it to the manufacturer s specification. Recondition and regap or replace the points as necessary. If the visual inspection doesn t reveal any problem, check any safety interlock switches that the engine or watercraft contains. Some outboard engines use prevent-start switches that prevent the engine from starting unless the gear shift is set in neutral. In some small watercraft (such as jet skis), a safety line connects the operator to the start switch. If the operator falls off the craft, the line pulls the key out of the switch and stops the engine. Test the operation of any such safety devices. Next, if the problem still hasn t been identified, you ll need to test the ignition system components. A spark test will determine whether the ignition system is producing a proper spark. Condensers, ignition coil windings, and electronic ignition systems can be tested for shorts to ground or opens with an ohmmeter. The condenser s output and capacitance and the output of the ignition coil windings can be tested with a special coil-condenser tester. The output of an electronic ignition system can be tested with a voltmeter. Checking Stop Circuits and Ignition Key Switches Many outboard engines are equipped with stop buttons or kill circuits. Some, particularly larger engines with electric starters, also contain ignition switches. These components must be checked if an ignition system fails to produce a proper spark. In an engine with a conventional ignition system, the kill circuit is often just a simple grounding switch. When pressed, the switch shorts the primary circuit to ground. A fault in the switch or the wiring will cause the system to fail to produce a spark. You can usually check the kill circuits in a conventional ignition system visually. In an electronic ignition system, the kill circuit also grounds the primary circuit. Usually, only one end of the capacitor is connected to ground. When the stop button is pressed, both ends of the capacitor are grounded. Current is prevented from reaching and charging the capacitor. To determine if a fault is present in the stop button or kill circuit, you ll need to bypass the kill circuit.

50 Outboard Engines 47 The procedure used to bypass and check the kill circuit of a 25 horsepower or 35 horsepower outboard engine is outlined in the following steps: Step 1: Step 2: Separate the three-wire connector between the ignition coil and the capacitor (power pack). Connect two jumper wires between the capacitor discharge terminals of both ends of the connector, as shown in Figure 34. This connects the capacitor to the ignition coils, but bypasses the kill circuit (the third terminal). FIGURE 34 To bypass and check the kill circuit of a 25 horsepower or 35 horsepower outboard engine, connect two jumper wires between the capacitor discharge terminals of both ends of the connector, as shown here. This connects the capacitor to the ignition coils, but bypasses the kill circuit (the third terminal). (Courtesy of the Johnson Division of the Outboard Marine Corporation) Step 3: Step 4: Connect a spark tester. (In a two-cylinder engine, connect the tester to both of the spark plug leads.) Crank the engine. If there s no spark, or if a spark jumps across only one gap of the spark tester, the kill circuit is okay. If a spark jumps both gaps of the spark tester, however, a fault is present in the kill circuit. The stop button and the wiring will have to be replaced to correct the fault. Tether line-type kill circuits can be tested by connecting a jumper wire to the kill terminals of the kill switch receptacle. An ohmmeter test can be conducted to check the ignition circuit in an engine that s equipped with an ignition key switch. If the ignition switch circuit tests faulty, use an ohmmeter to determine whether the fault is in the switch or the wiring.

51 48 Outboard Engines Follow these steps to perform the ohmmeter test: Step 1: Step 2: Step 3: Step 4: Insert the red (positive) ohmmeter lead into the third terminal of the ignition coil end of the three-wire connector. Connect the black (negative) ohmmeter lead to ground. Separate the four-wire connector between the magneto and the capacitor (power pack), and turn the ignition switch to the ON position. If the ohmmeter produces a reading of infinite ohms (open circuit), the switch and the wiring are okay. However, if there s a fault in the switch or the switch circuit, the ohmmeter will show a low resistance reading. To isolate the fault, disconnect the stop-circuit lead from the switch. If the fault is in the switch, the ohmmeter will show a reading of infinite ohms (open circuit). If the fault is in the wiring, the ohmmeter will show a low resistance reading (closed circuit). Testing Electronic Ignition Components If the results of the spark test are negative and you determine that the stop button/kill circuit or ignition switch and switch wiring aren t at fault, the other components of the ignition system must be tested. Some of these tests may be performed with an ohmmeter, while others are performed with a voltmeter. An ohmmeter set to read low resistance should be used to test the sensor or trigger coil for excessive resistance or shorts-to-ground. As shown in Figure 34, separate the four-wire connector between the magneto and the capacitor (power pack). Then, connect the ohmmeter leads between the sensor coil lead terminals of the magneto end of the connector. If the ohmmeter shows a reading of 40 ohms (+/ 10 ohms), the sensor coil is in good condition. If the ohmmeter reading doesn t fall within this range, the sensor coil will need to be replaced. Next, use an ohmmeter set to read high resistance to check the sensor coil for a short-to-ground. Connect the red (positive) meter lead to one of the sensor coil terminals of the magneto end of the connector, and connect the black (negative) meter lead to ground. Observe the meter reading at this time. Then, move the red meter lead to the other sensor coil terminal of the connector plug, and observe the meter reading. If you note any difference between the first meter reading and the second reading, then either the sensor coil or the sensor coil leads are shorted to ground. In this situation, the sensor coil must be replaced, or the defective lead must be repaired or replaced. An ohmmeter set to read low resistance is also used to test the magneto charge coil for resistance and shorts-to-ground. To check the charge coil resistance, connect the ohmmeter leads between the charge coil terminals of the magneto end of the four-wire connector. Unless the ohmmeter shows a reading of 575 ohms (+/ 75 ohms), the charge coil will need to be replaced.

52 Outboard Engines 49 To check the charge coil for shorts-to-ground, connect the ohmmeter leads between one of the charge coil terminals and ground. If you note any fluctuation in the reading when the red (positive) lead is moved from one charge coil terminal to the other, then the charge coil or the leads are shorted to ground. Note that when you test ignition system components, you should consult the manufacturer s service manual to determine the proper test readings you should get. Compare your measured values against the manufacturer s listed values to check for problems. Also, remember that resistance tests should only be performed when an engine is cool. If an engine is hot when you perform a resistance test, the readings may be inaccurately high. Remember that the resistance in an electrical circuit increases as temperature increases. Next, use a voltmeter to test the following components with the engine off: The sensor coil output The charge coil output The capacitor (power pack) output Note that the sensor coil, charge coil, and capacitor may also be tested with the engine running. However, this type of test requires special testing equipment that enables the engine to run with the connector plugs separated. In this type of test, the connector ends are plugged into a special adapter, and readings are taken from pinholes in the adapter. Use an ohmmeter to test the primary and secondary windings of the ignition coils for resistance and shorts-to-ground. You can perform these tests with the ignition coils on the engine. However, you must remove the ignition coils from the engine to test them for high voltage leaks and output power. These tests are performed with a special coil-condenser tester. Troubleshooting the Electrical System Remember that the electrical system of an outboard engine with an electric starter will typically include the following components: The starter system The charging system The battery All necessary cables, wiring, connections, and instrumentation The electrical system in a larger engine may also include an electrically operated hydraulic pump to run a power trim-and-tilt system, plus the necessary wiring and controls for the pump. The most common symptom of electrical system trouble is the failure of some component (such as the starter motor) to operate. There are numerous possible causes for such a failure, including a dead or defective battery or a faulty starter motor. However, the most common causes of

53 50 Outboard Engines electrical component failures are loose, dirty, corroded, or damaged wiring or connections. These conditions can prevent the battery from charging properly or from holding a charge when the engine is running. They can also prevent current from reaching the starter motor. Therefore, a careful visual inspection of the wiring and connections should be the first step in the troubleshooting process. The remaining procedures used to troubleshoot outboard engine electrical systems are exactly the same as those used to troubleshoot garden tractor systems. A detailed discussion of these procedures was provided earlier in your course. Troubleshooting the Fuel System Fuel system malfunctions are usually indicated by a loss of engine power or difficult starting. However, if the fuel system malfunctions in a way that prevents fuel from reaching the combustion chambers, the engine will be impossible to start. Therefore, when you re troubleshooting the fuel system, it s advisable to check out the entire system. This will eliminate the possibility that a fault may have more than one underlying cause. A compete check of the fuel system will include the following: A check of the fuel tank and supply A pressure-test of the remote fuel tanks and fuel hoses A carburetor check An inspection of the reed valves A check of the choke and primer solenoids A pressure-test of the fuel pump Now, let s look at each of these tasks in more detail. Checking the Fuel Tank and Supply Gasoline is an unstable substance. Over time, petroleum gum and varnish will develop in the fuel mixture, clogging the fuel filter screen and other small passages. This clogging restricts the flow of fuel, preventing the engine from running properly and making it hard to start. Water or dirt in the fuel tank will also interfere with engine operation. In twocycle engines, the oil-and-fuel mixture must also be correct to allow proper operation. Therefore, if you suspect a problem in the fuel system, the first step is to drain the fuel tank and flush it with clear gasoline or solvent. Then, refill the tank with a fresh fuel mixture. Carefully inspect a fuel tank visually for rust, as well as fuel or vapor leaks. A badly rusted or leaking tank must be replaced. Check the filler cap and gasket for wear, damage, or leaks, and replace the parts if necessary.

54 Outboard Engines 51 Fuel tanks that are mounted in the powerhead (as well as some small remote tanks) are equipped with air vent screws. Larger remote tanks are vented by one-way disc valves. These valves prevent fuel or fuel vapor from escaping from the tank, but allow air to enter the tank. If a vent screw is closed or clogged, or if a vent valve is clogged or stuck, a partial vacuum will build up inside the fuel tank when the fuel level drops. This will interfere with and eventually stop the flow of fuel out of the tank, causing the engine to lose power and stall. Powerhead-mounted fuel tanks are also provided with fuel shutoff valves. This valve must be open to allow fuel to reach the carburetor. Pressure-Testing Remote Fuel Tanks and Fuel Hoses If you suspect that a remote fuel tank or a fuel supply hose is leaking fuel or fumes, the tank and hose assembly should be pressure-tested to locate the leak. Fuel tank pressure tests can be performed with a gearcase pressure tester and a fuel tank adapter, both of which are shown in Figure 35. You ll also need a supply of compressed air to perform the test. FIGURE 35 The equipment needed to pressuretest a remote fuel tank is shown here. (Courtesy of the Johnson Division of the Outboard Marine Corporation) To perform a pressure test on a remote fuel tank or hose assembly, follow these steps: Step 1: Step 2: Remove the fuel filler cap and disengage the filler cap retaining anchor from the fuel tank. Remove the anchor from the filler cap. Empty the fuel tank into an approved safety container. Any fuel left in the tank during the pressure test may conceal the location of a leak. Step 3: Install the fuel tank adapter on the fuel tank as shown in Figure 36. Then, attach the filler cap (with the anchor removed) to the adapter. Step 4: Attach the gearcase pressure tester to the adapter fitting. Then, open the adapter fitting and the adapter air-release valve. The adapter air-release valve allows pressure in the fuel tank to reach the pressure tester gage.

55 52 Outboard Engines Step 5: Step 6: Step 7: Step 8: Attach the compressed air nozzle to the stem on the adapter. Then, pressurize the fuel tank with compressed air until the gage on the pressure tester reads 10 psi. Use short, quick bursts of compressed air to avoid over-pressurizing the tank. This will help prevent damage to the fuel tank or fuel supply hose. The coupling at the engine end of the fuel hose contains a balltype check valve that automatically closes when the hose is disconnected from the engine. Hold the end of the fuel hose below the top of the tank, depress the ball, and empty any remaining fuel in the hose into a container. Bring the air pressure in the tank back up to 10 psi. Then, close the adapter air-release valve and remove the pressure tester. Check the tank and hose assembly for leaks by immersing the tank and fuel hose assembly in water. Submerge the tank and hose assembly one portion at a time, and look for the presence of air bubbles. To check the fuel tank coupling, repeat the immersion test with the fuel hose removed from the tank. When the pressure test is completed, release the pressure in the tank by opening the adapter air-release valve. Do this before you attempt to remove the filler cap from the adapter. FIGURE 36 Shown here is a fuel tank pressure test adapter installed on a fuel tank. (Courtesy of the Johnson Division of the Outboard Marine Corporation) If the pressure test indicates that a fuel tank is leaking, replace the tank. In addition, if you find leaks in the upper housing (which contains the fuel hose connection, the air inlet valve, and the fuel level indicator), the upper housing gasket, or any component of the fuel hose assembly, the part should also be replaced. Manufacturers service manuals will contain complete instructions on how to disassemble, repair, and reassemble the fuel tank upper housing and fuel hose assemblies. After you replace or repair any parts, the pressure test should be repeated as described above to make sure that the leak has been fixed. If you fail to pressure-test the fuel supply system after repairs, you may unknowingly return a leaking fuel tank and fuel hose assembly to service. It isn t sufficient to simply refill the fuel tank with fuel to check for possible leaks. Leakage, particularly of fuel vapors, may occur only when the tank

56 Outboard Engines 53 and hose assembly becomes pressurized. Pressurization often occurs when the tank is exposed to sunlight or agitated. Servicing Carburetors If an outboard engine carburetor floods when the fuel valve is opened or the primer bulb is squeezed, the carburetor will need to be removed, disassembled, and cleaned. In order to remove the carburetor from most outboard engines, you ll usually need to disconnect the fuel line, the choke, and the throttle linkages, and remove the air silencer. In some cases, it may also be necessary to remove the manual starter, the electric starter, or the fuel pump. Complete instructions for carburetor removal will be included in an engine s service manual. When you disassemble the two-barrel carburetors found on larger engines, it s a good idea to make a note of the sizes of the high and intermediate orifices, as well as the idle air bleed orifice. This ensures that these components will be returned to their proper positions when the carburetors are reassembled. Size numbers will be stamped on the part. Use extra care when you remove the float chamber from the carburetor body, and when you remove the float and float arm assembly. These parts are delicate and easily damaged. When you remove the float valve and valve seat, take care to prevent damage to the threads in the carburetor body. Damage in this area will require that the entire body casting be replaced. Unless the choke or throttle valves are damaged or excessively worn, they shouldn t be removed. In most cases, the screws that hold the valves to the valve shafts are staked to prevent them from working loose. After the carburetor is disassembled, the parts can be cleaned. All carburetor parts may be cleaned in solvent, except for the float, float valve, and float valve seat. A special solvent should be used to remove the deposits of petroleum gum or varnish that often accumulate in the float chamber and on the float valve and seat. Once all the parts are clean, visually inspect them for any signs of pitting or corrosion. Any parts that are pitted or corroded will need to be replaced. During cleaning, thoroughly flush all of the passages in the carburetor body with solvent, then blow them out with compressed air (use no more than 30 psi of air pressure). Compressed air should also be used to dry the parts. Drying carburetor parts with a cloth can leave lint deposits that may cause problems after the carburetor is reassembled. Also, be sure to remove all traces of old gasket material and sealer from the gasket surfaces. When the gasket surfaces are clean, carefully inspect them for nicks, scratches, or distortions. If necessary, you can refinish the surfaces of the float chamber and the carburetor body by using a surfacing plate and an emery cloth to remove minor irregularities. Next, carefully inspect the float and float arm for damage or wear. Replace the cork floats if they re damaged or oil-soaked. Replace the float arm if you notice signs of wear in the hinge or in the area where the arm contacts the base of the float valve.

57 54 Outboard Engines If either the float valve needle or the valve seat is nicked, scratched, or worn, it must be replaced. The condition of the valve seat is critical to proper engine operation. Therefore, when inspecting it for wear, it s a good idea to use a magnifying glass. Also, note that because the float valve needle and the valve seat are a matched set, if either is worn and requires replacement, both parts must be replaced. If the tapered end of the low-speed needle is nicked, scratched, or worn, it must be replaced. Also, many manufacturers recommend that the needle packing be replaced, even if the old needle is still usable. Unless you discover signs of leakage, the core plugs and the lead shots should need no attention. Minor leakage may be corrected by placing a flat end punch in the center of the plug or lead shot and giving it a sharp tap with a mallet. If leaking persists, however, the core plug or lead shot must be replaced. Once you ve completely inspected and cleaned all the parts, the carburetor is ready to be reassembled. When reassembling a carburetor, remember that you must always use new gaskets, O-rings, and sealing washers, even if the originals appear to be in perfect shape. Reassembling a carburetor with used gaskets, O-rings, or washers may cause leaks to develop soon after the engine is back in service. Carburetor repair kits that contain all the necessary replacement gaskets and parts are available from outboard engine manufacturers. After the float and float valve assembly have been replaced, check the position of the float with a special gage. The float in a two-barrel carburetor must also be checked for a proper drop, as shown in Figure 37. If the drop is incorrect, adjust it as necessary. Check the manufacturer s service manual to determine any carburetor specifications that you may need to measure. Also, when installing the float chamber, refer to the service manual for the proper torque settings. Insufficient torque on the float chamber screws may result in leakage. FIGURE 37 This illustration shows how to check the drop of a float on a twobarrel outboard engine carburetor. (Courtesy of the Evinrude Division of the Outboard Marine Corporation) When you re reconnecting the fuel lines, check the condition of all of the hoses and clamps, and replace them as necessary. On an engine that uses a remote fuel tank, after you mount the carburetor, reconnect the fuel supply hose and squeeze the primer bulb to check for leaks.

58 Outboard Engines 55 Inspecting and Servicing Reed Valves The condition of the reed valves is critical to proper two-cycle engine operation. The reed valve assembly should be clean and free of petroleum gum or varnish deposits. The reeds must lie perfectly flat against the valve plate. To inspect and clean reed valve assemblies, it s usually necessary to remove the intake manifold. When you re disassembling a reed valve assembly, be careful not to bend the reeds or the reed stops. Bent or damaged reeds can t be repaired. If they don t lie perfectly flat against the plate, they must be replaced. If the reeds require replacement, it s also a good idea to replace the reed stops, particularly if the leaves are broken. If the reed valve plate shows any signs of distortion or wear, it should also be replaced. When remounting reed valve assemblies and intake manifolds on the powerhead, always use new gaskets. Make sure that the gasket surfaces are clean, free of old gasket material, and in good condition. Consult the manufacturer s service manual to determine the proper torque settings. Checking Choke and Primer Solenoids Engines that are equipped with electric starters usually contain solenoidactuated chokes. Some V-4 engines also use solenoid-actuated primer systems that are controlled by their ignition switches. As a rule, these solenoids need very little attention. The plungers should be kept clean so that they can move freely in the solenoid housing. However, the plungers shouldn t be lubricated, since lubrication causes dust and dirt to adhere to the plunger. A solenoid can be checked, if necessary, by connecting an ohmmeter between the solenoid leads. The ohmmeter should be set to read low voltage. Generally, choke solenoids should register a maximum resistance reading of between 2 ohms and 5.5 ohms. Pressure-Testing the Fuel Pump Fuel pump pressure tests are performed only on engines that use remote fuel tanks. Since the engine must be running during the test, the engine must be on a boat or in a test tank. To obtain accurate test results, the fuel tank must be located no more than two feet below the level of the fuel pump. Before conducting the test, check to make sure that the fuel tank s air vent is open and operating properly. Negative or positive pressure in the fuel tank will affect the test results. Next, install a fuel pump pressure gage between the fuel pump and the carburetor. With the engine running, the gage should register the minimum readings specified in the manufacturer s service manual. The following table shows the typical minimum readings that should be obtained. If you don t get these readings, the fuel pump is defective and needs to be replaced.

59 56 Outboard Engines Table FUEL PUMP PRESSURE TEST VALUES Engine Speed Pressure Reading 600 rpm 1 psi (7 kpa) 2,500 to 3,000 rpm 1.5 psi (10 kpa) 4,500 rpm 2.5 psi (17 kpa) Troubleshooting Mechanical Problems in the Powerhead In an outboard engine, mechanical problems in the powerhead can cause hard starting and loss of power. For example, reduced compression can be caused by a blown or leaky cylinder head gasket; excessive glazing of the cylinder walls; or broken, worn, or stuck piston rings. Any of these mechanical problems can make it difficult (or impossible) to start an engine. Low compression can also cause a loss of power due to incomplete fuel combustion. Starting problems may also be experienced if water gets into the crankcases or the cylinders as a result of a leaky gasket or a cracked engine block. Other conditions caused by mechanical problems in the powerhead include Knocking Severe vibration Unusual noises Binding Overheating Knocking, for example, can occur as a result of a loose or worn piston pin, a bent or twisted connecting rod, excessive wear on the cylinder wall or piston, or a loose flywheel. Any of these conditions may also cause severe engine vibration. Vibration can also be caused by a damaged propeller or worn engine isolation mounts. Overheating may be caused by a faulty thermostat or a blockage of the powerhead water passages. It can also occur as a result of a defective water pump or a clogged water intake. Now, let s look at some of the troubleshooting techniques used to service the powerhead. Checking the Compression The first step when troubleshooting an outboard engine powerhead is to perform a compression check. This test procedure was covered in detail earlier in the section on engine tune-ups, but we ll review it briefly here. Remember that you must disconnect the ignition system before testing to prevent the engine from starting accidentally.

60 Outboard Engines 57 To perform the compression test, turn the engine over by hand and gage the amount of compression in the cylinders. There should be a lively bounce as each piston passes top dead center (TDC). In general, the compression is too low if the engine doesn t bounce well as each piston passes TDC, and is too high if it s hard to pull past TDC. If you use a compression gage to perform the test, a difference of more than 10 psi between cylinders indicates a problem. Also, if the compression reading is between 10 psi and 15 psi less than the optimum compression specified in the manufacturer s service manual, a problem condition exists. Whichever test method you use, be sure to check the compression in each cylinder. If you observe any problem conditions during your test, you ll need to remove the cylinder head (or heads) and the exhaust cover to determine the cause of the problem. If the compression of one or more cylinders is too low, check the condition of the cylinder walls, pistons, and piston rings. If the compression is too high in one or more cylinders, check for an excessive buildup of carbon on the cylinder head or piston head. Inspect the exhaust ports, cylinder head, pistons, and piston rings. If you find excessive carbon deposits, the powerhead will need to be disassembled and cleaned. Checking the Cooling System If an engine is overheating or if the flow of water through the powerhead appears to be reduced, it s a good idea to start troubleshooting with a thorough check of the cooling system. The typical outboard engine is equipped with a small water outlet located immediately above the idle exhaust relief. This outlet is called a cooling indicator or an overboard indicator. Heated water will be discharged from this outlet when the cooling system is functioning properly. If the amount of heated water discharged from the overboard indicator is reduced, it may be the result of any of the following problems: A sticking or faulty thermostat A blockage in the powerhead cooling passages or lower unit water tube A faulty water pump A clogged water intake Any reduction of water flow through the powerhead will cause the engine to overheat. However, note that an engine that s equipped with a thermostat will produce a small amount of water discharge until it reaches its operating temperature and the thermostat opens. Therefore, in order to properly check an outboard engine s cooling system, the engine should be allowed to run for at least five minutes before testing. Then, to ensure that the engine is operating within its optimum temperature range, check the powerhead temperature with wax testing sticks. If an engine is overheating, the first thing that should be checked is the water intake. If the water intake is clear and free of clogs or blockages, look at the thermostat next (if the engine has one). To test a thermostat, you can remove it from the engine and submerge it in a pan of hot water. The thermostat should open when the test water reaches the thermostat s

61 58 Outboard Engines rated temperature. However, since thermostats are very inexpensive, it s usually a more effective troubleshooting procedure to simply replace the thermostat if you suspect that it s faulty. If the overheating problem persists after you replace the thermostat, there may be trouble in the lower unit. To check the water pump and the water tube, you ll need to remove the gearcase. We ll discuss the trouble shooting of the lower unit a little later in the study unit. Correcting the Problem of Binding An engine is said to be binding when it s difficult or impossible to turn over. The flywheel should always turn smoothly and evenly, with a minimum of resistance. There should be some resistance only when a piston passes TDC. If an engine appears to be binding when you test it, never force the engine to turn over. This may cause severe damage to internal engine parts, as well as to the starter mechanism. To prevent the engine from starting when you re checking for binding, disconnect the spark plug wires or disconnect the magneto from the power pack. Binding may occur for a variety of reasons. The most common cause is mechanical damage in the gearcase or powerhead components. Broken piston rings and damaged bearings (connecting rod bearings and crankshaft bearings) are typical powerhead problems. Binding may also occur if the piston rings are too large for a cylinder (for example, if the wrong rings were accidentally installed on the piston). Removing and Disassembling the Powerhead If you discover a mechanical problem in the powerhead, the powerhead will need to be removed, disassembled, cleaned, and repaired. Because there are so many different makes and models of outboard engines, we can t provide detailed instructions on how to remove and disassemble every type of powerhead. However, we can give you general procedures that are applicable to most outboard engines. Further information about particular models can be found in manufacturers service manuals. As a general rule, in order to remove a powerhead from the exhaust housing, you ll need to remove the following components first (if applicable): The fuel tank (if mounted on the powerhead) The carburetor(s) The manifold and leaf valve assembly The fuel pump and fuel lines The flywheel and armature plate The power pack(s) and/or ignition coils The spark plugs The starter (or starter motor and solenoid)

62 Outboard Engines 59 On some larger engines, to make the powerhead lighter and more manageable, the cylinder heads and exhaust covers should also be removed. Once these components have been removed from the powerhead, the powerhead can be disconnected from the exhaust housing. This may involve the removal of part of the lower engine cover to gain access to the powerhead mounting screws. The powerhead mounting screws are often located near the base of the manual steering arm or steering linkage. Remove the mounting screws, then lift the powerhead off the exhaust housing. For larger engines, this step may require the use of a hoist. When you place the powerhead on your workbench, be careful not to damage or bend the inner exhaust tube, which often remains attached to the powerhead. The studs in the powerhead can be protected by screwing a nut over the end of each stud until the nut is flush with the end of the stud. Once the powerhead is safely placed on your workbench, you can begin to disassemble and inspect its parts. For the most part, powerhead disassembly is a straightforward procedure. Detailed instructions will be provided in manufacturers service manuals. Most manuals will contain exploded diagrams, with all of the engine parts identified. These diagrams are very helpful during both the disassembly and reassembly process. Note that some repairs may not require the complete disassembly of the powerhead. For example, the upper and lower main crankshaft seals can usually be replaced without disassembling the powerhead. Usually, the replacement of the upper crankshaft seal doesn t even require the removal of the powerhead from the engine. However, if you need to service the cylinder or pistons, you ll need to completely disassemble the powerhead. When disassembling any engine, it s a good idea to have several clean, covered containers available that you can use to hold small parts, such as fasteners and bearings. Containers help to keep small parts clean, safe, and organized. You can use a different container to hold the parts for each powerhead area. As we ve mentioned several times throughout this course, parts should always be replaced in the exact same position from which they were removed. This is especially true for moving parts, such as needle bearings and connecting rod caps. It s also important to tag or identify larger parts during the disassembly procedure. For example, use a grease pencil to mark the cylinder number on each piston so that you can remember where each piston needs to be reinstalled. Connecting rods should also be tagged so that they can be reassembled with the correct piston. To prevent larger parts from becoming contaminated with dirt or old oil, keep your work area clean. Start the disassembly by removing the cylinder head(s) and exhaust cover(s), if they haven t already been removed. If the piston(s) need to be removed, the crankcase must be removed first to allow access to the connecting rod caps. Be careful to protect the gasket surfaces of the crankcase and the cylinder block from damage. Remember that there usually is no gasket between the cylinder block and the crankcase.

63 60 Outboard Engines Once the powerhead is disassembled, you ll need to clean the components thoroughly with solvent, then blow them dry with compressed air. Pay particular attention to cleaning the oil and water passages. When all the parts have been cleaned, carefully inspect them for wear and damage. As you examine the components, try to identify the source of the mechanical trouble. The following is a general procedure that can be used to inspect and rebuild the powerhead components. The rebuild procedures that were discussed earlier in the course in detail will all apply to outboard engines. However, we ve provided you with a brief review of the procedures here. Step 1: Step 2: Step 3: Step 4: Step 5: Step 6: Step 7: Step 8: Inspect the cylinder walls carefully for scoring or scuffing, then measure their roundness and taper. Compare these measurements to the specifications listed in the manufacturer s service manual. Deglaze the cylinder(s) with a honing tool. Resize the cylinder(s) to specifications, if necessary. After the cylinders have been deglazed or resized, clean the cylinder block with soap and water. Then, clean the block again with solvent, and blow the block dry with compressed air. Check the exhaust ports for excess carbon deposits. Carefully scrape any carbon deposits from the ports, if necessary. Remember that even the slightest amount of carbon can interfere with the flow of exhaust gases out of the cylinders. Check the piston(s) for wear, and check to see whether the piston rings are sticking as a result of excessive carbon accumulation. Clean any petroleum gum and varnish deposits off the pistons with cleaning solvent. Carefully scrape any carbon deposits from the top of each piston. Measure the pistons and compare your measurements to the specifications in the manufacturer s service manual. Install new rings on the pistons. Clean and carefully inspect the crankshaft and the crankcase bearings. Bearings that exhibit any signs of corrosion, wear, or excessive discoloration should be discarded and replaced. When all the parts have been cleaned and serviced, you can reassemble the powerhead. Always use new gaskets when you reassemble a powerhead, and remember to thoroughly clean any old gasket material or cement off the gasket surfaces. Unless otherwise specified by the gasket manufacturer, lightly coat both sides of the gaskets with gasket sealing compound. Before the cylinder head is reinstalled, it should be resurfaced to remove any high spots from the gasket face. Then, reinstall the cylinder head using a new gasket. Lightly coat the gasket on both sides with gasket sealing compound unless otherwise specified. The cylinder head bolts should then be tightened in the recommended sequence to the manufacturer s recommended torque value.

64 Outboard Engines 61 Once you ve identified and repaired the mechanical problem and reassembled the powerhead, the engine operation should be tested, either in a tank or on a boat. Following the test, and after the engine has cooled to the touch, the cylinder head bolts should be retorqued in the proper sequence. Also, note that when a powerhead has been disassembled and serviced, the engine must be broken in again as if it were new. The procedure for breaking in a new engine was described earlier in the study unit. Troubleshooting Mechanical Problems in the Lower Unit Now, let s turn our attention to mechanical problems in the gearcase and lower unit. The problems that are commonly associated with malfunctions in the gearcase are the following: Severe engine vibration Overheating A noisy or seized right-angle drive Inability to shift gears or remain in gear Severe engine vibration is often caused by a damaged or loose propeller, or worn or loose rubber isolation mounts. Vibration may also occur if the engine isn t securely mounted on the boat. The stern brackets must be tightly clamped to the transom. Overheating is often the result of a clogged water intake, a defective water pump, or a damaged water tube. A right-angle drive problem may occur due to worn or broken gears, a damaged gearcase, or inadequate lubrication. A gear shifting problem may be caused by the improper adjustment of the gear shift mechanism or by problems in the gearcase. Now, let s take a closer look at the troubleshooting methods that are used to isolate and correct these problems in the lower unit. Correcting Engine Vibration The most common cause of vibration in an outboard engine is a damaged propeller. Examine the propeller for bends, cracks, or breaks in the blades, and replace them if necessary. Never attempt to repair a cracked or broken blade by welding. However, you can remove minor nicks by filing. If you do file out a nick, be careful to retain the original shape of the blade edge. Also, avoid removing too much metal the blades will become unbalanced. For this reason, badly nicked propellers must be replaced. Another cause of engine vibration is loose or worn rubber isolation mounts. An outboard engine contains a number of rubber mounts that isolate the exhaust housing from the stern bracket. The rubber mounts absorb engine vibrations and prevent them from being transmitted to the boat through the transom. The number of rubber mounts an engine contains depends on the engine model. For example, a typical 25 horsepower or 35 horsepower engine has six mounts. These mounts include two upper side mounts, two lower side mounts, an upper thrust mount immediately below the powerhead, and a lower thrust mount between the exhaust

65 62 Outboard Engines housing and the lower stern bracket. You can see examples of these mounts in Figure 11 at the beginning of this study unit. To inspect the lower thrust and side mounts, remove the cover plates as shown in Figure 38. Depending on the engine, you may need to remove the powerhead and the lower engine cover to inspect the upper side and thrust mounts. Any loose mounts should be tightened, and worn mounts should be replaced. FIGURE 38 The locations of the thrust mounts on an outboard engine are shown here. (Courtesy of the Johnson Division of the Outboard Marine Corporation) Servicing the Water Pump Overheating is commonly caused by a faulty water pump. In order to service an outboard engine water pump, you ll usually need to remove the gearcase from the exhaust housing. Gearcase removal doesn t require the removal of the powerhead. However, to prevent accidental engine starting, the ignition system should be disabled. If you re working on an engine with an electric starter, the battery should also be disconnected to prevent the accidental engagement of the starter motor. The procedure used to remove and service the water pump will vary with the engine model. Therefore, you should carefully follow the instructions in the manufacturer s service manual when you remove the gearcase. The procedure we ll describe here can be used to remove the water pump from most engines. Figure 39 shows the gearcase-attaching hardware of a 35 horsepower, two-cylinder engine. This is the same engine that was shown earlier in Figure 11. Before you remove the attaching screws and nuts, you must remove both the port and the starboard water intake screens. This step must be done first in order to gain access to the shift rod connector. Then, remove the keeper and the upper connector from the upper shift rod to allow the gearcase to be lowered (Figure 40).

66 Outboard Engines 63 FIGURE 39 The gearcase attaching hardware of a 35 horsepower engine is shown here. (Courtesy of the Johnson Division of the Outboard Marine Corporation) FIGURE 40 Remove the keeper and the upper connector from the upper shift rod to allow the gearcase to be removed. Figure 40A shows a close-up view of the shift rod connection. Figure 40B shows the removal of the upper connector and the keeper. (Courtesy of the Johnson Division of the Outboard Marine Corporation)

67 64 Outboard Engines As you lower the gearcase off the midsection, be careful to prevent damaging the driveshaft as it emerges from the exhaust housing. Also, depending on the engine model, the water tube that connects the water pump to the powerhead may come away with the gearcase. Figure 41 shows the water tube still attached to the water pump impeller housing. FIGURE 41 Shown here is the water pump of a 35 horsepower outboard engine with the water tube still attached. (Courtesy of the Johnson Division of the Outboard Marine Corporation) Disassembling the water pump is a simple matter of first removing the water tube and water tube grommet, then removing the impeller housing attaching screws. The water pump impeller housing is then lifted up the driveshaft and removed. Figure 42 shows a water pump with its housing removed. You can now remove the impeller by lifting it up the driveshaft. Unless the impeller pin is damaged, you should save it. The gasket that lies between the housing and the impeller plate and the gasket that lies between the impeller plate and the gearcase should both be discarded. FIGURE 42 Shown here is a water pump with its housing removed. (Courtesy of the Johnson Division of the Outboard Marine Corporation)

68 Outboard Engines 65 Next, inspect the impeller, impeller housing, cup, and the impeller plate for wear, damage, or corrosion. Replace parts as necessary. If the impeller housing seal leaks, allowing water to escape from the pump chamber and reducing pump pressure, the seal should be replaced. To install a new impeller housing seal, you ll need to use the special tool shown in Figure 43. Place the housing upside-down on a wooden block that has a 3 4 -inch diameter hole cut in it. The hole will accept the end of the tool as the seal is seated. FIGURE 43 A special tool is needed to install a new impeller housing seal. (Courtesy of the Johnson Division of the Outboard Marine Corporation) To reassemble the water pump, apply a light coating of gasket sealing compound to both sides of new impeller plate gaskets. These gaskets aren t interchangeable and must be installed in the proper positions in order for the pump to function. Install the gaskets. Then, apply a dab of needle bearing grease to hold the impeller pin in place on the driveshaft, and slide the impeller into place. Insert a new water tube grommet into the water outlet on the impeller housing. If the impeller cup was removed from the housing in order to replace the seal, reinstall it in the housing. Then, slide the housing down over the driveshaft. Before you fit the housing over the impeller, apply a little oil to the tips of the impeller blades. Slowly rotate the driveshaft in a clockwise direction as you lower the housing over the impeller. This must be done to ensure that the impeller blades are properly positioned in the housing. (The pump housing is off-center with respect to the driveshaft and impeller.) Next, tighten the pump impeller housing screws, and install the water tube in the grommet in the pump outlet. Finally, install the gearcase on the exhaust housing.