EXHAUST SYSTEM GENERAL

Transcription

1 EXHAUST SYSTEM A GENERAL

2 Table of Contents Page Exhaust System Requirements A-1 Determining If Exhaust Elbow Risers Are Required A-1 MCM (Stern Drive) Engines With Thru Transom Exhaust A-1 MIE (Inboard) Engines A-2 Exhaust Hose Connection A-2 Exhaust Tube Requirements A-3 7A-0 - GENERAL

3 Exhaust System Requirements IMPORTANT: It is the responsibility of the boat manufacturer or installing dealer to properly locate the engine and install the exhaust system. Improper installation may allow water to enter the exhaust manifolds and combustion chambers and severely damage the engine. Damage caused by water in the engine will not be covered by MerCruiser Limited Warranty, unless this damage is the result of defective part(s). Determining If Exhaust Elbow Risers Are Required On all engines to determine if exhaust elbow risers are required, take measurements (a) and (b), with boat at rest in the water and maximum load aboard. Subtract (b) from (a). If (a) minus (b) is less than specified in chart, select appropriate size exhaust elbow riser kit and exhaust extension kit that will correctly position exhaust elbow Exhaust Elbow Measurement a - From Waterline To Top Of Transom b - From Highest Point On Exhaust Elbow To Top Of Transom MCM (Stern Drive) Engines With Thru Transom Exhaust When designing and installing exhaust system, the following must be observed: Minimum Hose Size Model Single Outlet Dual Outlet All (Except Magnums) 5 in. (127 mm) 4 in. (102 mm) Magnum 4 in. (102 mm) 1. Exhaust flanges must be of proper size to accommodate 4 in. (102 mm) I.D. exhaust hoses. They must also be equipped with internal water shutters, and use an exhaust flapper over each outlet. 2. The exhaust hoses and pipes must not be higher than exhaust elbows at any point. 3. The exhaust outlet must be located so that a minimum of 1/2 in. (13 mm) drop per foot (305 mm) downward pitch exists in the exhaust hose from the engine exhaust elbow to the outlet. (This is an American Boat & Yacht Council recommendation.) The drop must be constant so that a low spot does not exist at any point in the exhaust hose. 4. Exhaust outlet must be slightly above the waterline with boat at rest in the water and full load aboard. 5. Back pressure must not exceed 4 in. (102 mm) of mercury when measured with a mercury manometer to exhaust elbow outlets. Model All (a) Minus (b) Must Be at Least 13 In. (330 mm) GENERAL - 7A-1

4 MIE (Inboard) Engines When designing and installing exhaust system, it is very important that the following additional points be taken into consideration: 1. System layout and construction must prevent cooling system discharge water from flowing back into engine and also must prevent seawater from entering engine via exhaust at any point. 2. The exhaust hoses and pipes must not be higher than exhaust elbows at any point. 3. The exhaust outlet (for routing exhaust to outside of boat) must be located so that a minimum of 1/2 in. (13 mm) per foot (305 mm) downward pitch (drop) exists in the exhaust hose or pipe from the engine exhaust elbow to the outlet, with a minimum drop of 4 in. (102 mm) overall. (This is an American Boat & Yacht Council recommendation.) The drop must be constant so that a low spot does not exist at any point in the exhaust hose or pipe. 4. Exhaust outlet must be slightly above the waterline with boat at rest in the water and full load aboard. Exhaust outlet should be equipped with an internal shutter to prevent seawater from running back into exhaust system. The use of an exhaust flapper on each outlet also is recommended. 5. System must not cause excessive back pressure. Back pressure MUST NOT exceed 4 in. (102 mm) of mercury when measured with a mercury manometer at exhaust elbow outlets. Minimum exhaust hose sizes are given in chart. Exhaust Hose Connection 1. Exhaust hoses must be connected to exhaust elbows so that they do not restrict the flow of discharge water from the elbow. If hoses are connected incorrectly, a hot spot in the hose can occur, and can eventually burn through. b a a - Correct Connection b - Incorrect Connection Exhaust hoses must be secured at each connection with two hose clamps. Minimum Hose Size Model Single Outlet Dual Outlet All (Except Magnums) 5 in. (127 mm) 4 in. (102 mm) 7A-2 - GENERAL

5 Exhaust Tube Requirements IMPORTANT: When installing thru-transom exhaust, it is recommended that the exhaust bellows on the transom assembly be removed. This is necessary to avoid creating a vacuum at the exhaust outlet in the propeller at higher boat speeds. This vacuum could degrade propeller performance on some boats. IMPORTANT: When installing thru-propeller exhaust: With any application, installation of an exhaust tube will increase exhaust noise. With Bravo One and Bravo Two Drives an exhaust tube MAY BE INSTALLED for a slight increase in performance. With a Silent Choice Exhaust System the exhaust bellows must be removed and an exhaust tube MUST BE INSTALLED. With most Bravo Three Drive Models an exhaust tube MAY BE INSTALLED for a slight increase in performance. On the following Bravo Three Models, the exhaust bellows must be removed and an exhaust tube MUST BE INSTALLED: MCM 7.4LX EFI MCM 7.4LX MPI MCM 454 Magnum MCM 454 Magnum MPI MCM 502 Magnum MPI GENERAL - 7A-3

6 THIS PAGE IS INTENTIONALLY BLANK TO ALLOW FOR CORRECTIONS OR ADDITIONS AT A LATER DATE 7A-4 - GENERAL