Substantial transom water leak, 1987 Four Winns Cobra 4.3

[Knoxsyncro]

1987 Four Winns Horizon 180. I’m the second owner, always trailer kept. Substantial water leak through transom when at rest, not while underway. At the ramp, out drive submerged, I could hear the water pouring in. Later, a poor quality video confirmed that. I’m showing an image of wear it comes in. The stainless trapezoid plate.
A little history. I may have had a slow leak, but never enough to worry about. A month later, on the next trip out, I had the gusher. The bilge pump could stay ahead, but it was concerning.
My proposed repair is to do the out drive reseal. I understand that the transom could be rotten or that the Y pipe could have a hole.
Suggestions for other possibilities?

 

[Lou C]

Pull the drive & check the driveshaft bellows first…these I/Os require regular maintenance esp the drive pull & greasing gimble & ujoints and replacing bellows

 

[Knoxsyncro]

Thanks. I meant to add that I’ve pulled the drive and the drive bellows looked dry, but greasy.
I haven’t pulled the gimbal housing yet.

 

[Gonetofish247]

Let me know when you figure it out!

 

[Biggvs_Richardvs]

I had something similar and it turned out to be the exhaust "Y" wasn't properly sealed in the back. Had to pull the engine out to re-do it, but once you get the engine out it's a pretty striaghtforward job.

 

[Don't Panic!]

No matter the problem, the solution is going to involve pulling the drive and engine out of the boat. Once the engine is out, pull the whole transom plate and go from there. Any rot issues will be easier to see, and you'll be able to inspect everything.

I had a leak at that same point and fought the idea of pulling the engine, but ultimately did. It's not that bad a job, way easier than a car. Just need a high beam to lift the engine high enough to clear the transom.

In my case I don't know exactly what the problem was, but I replaced every seal I could while I was in there, tightened everything back up and it's working fine now. All day in the boat and not a drop out the drain plug afterwards.