Boat Exhaust

[600hp]

Hope someone can help. I just bought a 1989 bayliner that is very tough to start in the water. When I use muffs on it when its outside the water it cranks easy and starts without a problem. As soon as I put it into the water it will only crank if my battery is 100% charged. When I go to start it it seems like the battery is dead because it will only turnover slowly... but if I pull it out of the water it will turnover easily and start right up. I think it has something to do with the aftermarket exhaust that someone custom made. The exhaust is two openings underwater will a rubber flap on each. It is almost like the exhaust fills with water and therefore making it very hard to turn over.

What can I do to making my boat start easier while in the water??
Maybe something like a one way valve??

[Corpus Skipper]

That's probably your problem. Underwater exhausts should have a relief above the water line for low speed operation/ starting.

[600hp]

Is a relief something that I can install myself. If so where can I get them. This is my first boat so if I ask something dumb than take it easy on me

[lewisboats]

custom exhast will probably mean a custom relief. Take the boat to a muffler shop, preferably one that does headers and custom exhausts and tell them what you need. It will probably be something like a racing dump that they will come up with. They ain't cheap either...(the bad news)

Steve.