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Exhaust conversion to thru-hull
I have a boat fitted Mercruiser I/O 5.0 V8/ Alpha I with the usual exhaust
manifold-thru prop setup. This is operated in sal****er and typically the shutters, exhaust manifolds and elbows and exhaust pipe give way about every 3 years. This is quite a big ticket, especially with the exhaust pipe part which requires the engine to be removed. Using a closed freshwater cooling system can take the manifolds out of the equation, but the elbows and exhaust pipe remain exposed. Am thinking of putting in the closed cooling systems and using a thru-hull exhaust system. This leaves only the exhaust elbows to contend with. Easier and cheaper to maintain-yes??? Question is what do I need and how to go about putting in a thru-hull exhaust system. For one, I will need the thru-hull exhaust outlet with its flapper. Raw water will continue to be delivered to the elbows and mixed with the exhaust at exit. 1. Do I need 2 outlets? 2. What is the mounting point of the outlets, at waterline, below or above and by how much? 3. Do I need some kind of muffler/exhaust box or a direct connect to the elbows will do? Thanks in advance. PS Tan |
#2
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Exhaust conversion to thru-hull
I have done what you are talking about on two boats. This is what worked for
me. 1. I used two outlets, one would do but would be hard to arrange the exhaust ducting in the usually short space between the engine and transom. I would use two. 2.Usually just above the water line, it ca be partly below but should have some section of it exposed to air. However, you have to use good judgement here in assessing the risk of sinking should your exhaust piping become dislodged from the thru hull. Make sure to use some "Salisbury" type flappers for backwash and some flooding protection in case of the dislodged deal above. 3. Yes, on the muffler. From the elbows use a section of rubber exhaust hose, then for routing the use fiberglass tubing (see west marine catalogue or other) . For the muffler, I have built a couple of sets out of fiberglass based loosely on the baffling concept used by Flowmaster, an automotive performance? muffler. Finally rubber coupling to the transom thru hulls, use double ss hose clamps as all joints. I would use 3" system all the way, I think your riser outlets will be 3" as well. If you fabricate your muffler, you can custom fit it so that one or two bends in the exhaust ducting can be eliminated. Best of all is the sound of a lightly muffled V8 that's how a boat should sound. It was great music for trolling. For building the muffler, I made a plywood female mold which formed three sides and allowed me to arrange the baffling easliy before placing the fourth side on. My mufflers were rectangular in crosssection. I used mostly CSM and ortho resin. The baffling helps stop the flat sides from druming as well. That ought to give you some ideas so you can build your exhaust system. Good luck. -- Ron White My boatbuilding website is: www.concentric.net/~knotreel |
#3
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Exhaust conversion to thru-hull
Thanks.
That certainly helps in making my move towards a thru-hull system. My exhaust parts look like they are due soon. Tan PS "Ron White" wrote in message ... I have done what you are talking about on two boats. This is what worked for me. 1. I used two outlets, one would do but would be hard to arrange the exhaust ducting in the usually short space between the engine and transom. I would use two. 2.Usually just above the water line, it ca be partly below but should have some section of it exposed to air. However, you have to use good judgement here in assessing the risk of sinking should your exhaust piping become dislodged from the thru hull. Make sure to use some "Salisbury" type flappers for backwash and some flooding protection in case of the dislodged deal above. 3. Yes, on the muffler. From the elbows use a section of rubber exhaust hose, then for routing the use fiberglass tubing (see west marine catalogue or other) . For the muffler, I have built a couple of sets out of fiberglass based loosely on the baffling concept used by Flowmaster, an automotive performance? muffler. Finally rubber coupling to the transom thru hulls, use double ss hose clamps as all joints. I would use 3" system all the way, I think your riser outlets will be 3" as well. If you fabricate your muffler, you can custom fit it so that one or two bends in the exhaust ducting can be eliminated. Best of all is the sound of a lightly muffled V8 that's how a boat should sound. It was great music for trolling. For building the muffler, I made a plywood female mold which formed three sides and allowed me to arrange the baffling easliy before placing the fourth side on. My mufflers were rectangular in crosssection. I used mostly CSM and ortho resin. The baffling helps stop the flat sides from druming as well. That ought to give you some ideas so you can build your exhaust system. Good luck. -- Ron White My boatbuilding website is: www.concentric.net/~knotreel |
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