Identifying water leak (have picture)

[jpoe6]

I have a 1990 thundercraft with 4.3l omc cobra engine and outdrive. I've always only dealt with mercruiser so Im a bit new to the omc thing. When I backed the boat into the water on the trailer I noticed it started taking water on. There was a steady steam of water coming in
to the back of the boat from a silver plate that has a hole and what looks like two bolts coming through. The plate is almost to the very
bottom of the transom and below the engine. I attached pictures and was wondering if anyone could tell me what this plate is there for, and where the hole leads. I'm assuming I'm in need of a bellows job? Which leads to my last question. The exhaust bellow has several slits in it facing downward. I've done some research and found that these are supposed to be there to help with back pressure? i just don't
understand how the bellow can have holes or slits in it and not allow water in the boat? thanks for any help in advance.

 

[bruceb58]

Re: Identifying water leak (have picture)

The bellows you are looking at are the exhaust bellows and there are supposed to be slits in it. What feeds those bellows is the exhaust pipe which connects up to your riser/manifold so no water will enter your boat. You could actually remove that bellows and no water would enter your boat.

The bellows above that is the u-joint bellows which could leak water into your boat if it leaks. Pull the drive and see if you have water in those bellows.

If no water in the u-joint bellows, you could get water through the shift tube if its connection failed but not very likely.

Most common problem is the worst and that is leakage due to a rotten transom.

 

[a70eliminator]

Re: Identifying water leak (have picture)

The silver plate in your photo is a load bearing plate, two transom adapter mounting studs come through the plate and there are two nuts above that you can't see without an inspection mirror. the plate just spreads the load as the transom adapter nuts are tightened.
If your bellow was leaking water would fill the flywheel housing and leak out through a hole at the bottom, if the hole was plugged water would continue to fill till it leaked from the starter housing drain, if your water is no doubt comming in around that transom adapter then your pretty much comitted to pull the engine and drive to repair transom rot. Hopefully the water is spewing from the hole at the bottom of the flywheel housing that usually has hose connected and the hose is just missing, if thats the case a new bellow will probably fix it.
One other thing to check would be the trim sensor wire harness that comes through a hole in the transom directly above that plate, if it were missing it would leave a hole in the transom right at or just slightly above the water line and backing into the water on the trailer could dunk it and take on water that would come in right there.

 

[jpoe6]

Re: Identifying water leak (have picture)

Thanks guys a lot for the quick response. A70eliminator, the first thing Im going to check is for that trim sensor wire harness.
That would makes a lot of sense, because I ran the boat for several minutes on the trailer which was backed into the water. It was right before I went to launch that I had the truck back me in further and thats when I noticed the leak. So I'm hoping that the several mins it was running prior to being backed completely in, that the hole was above the water line. It sounds like that would be the easiest fix to so I will keep my fingers crossed. Thanks for the response