there is water leaking in from a hole on the plate attached to transom

I have a1990 four winns candia and behind the motor there is a plate attached to transom on this plate at the bottom is a hole and water is pouring in through it. this hole is just above the drain plug. Im taking the rear drive off this week to replace the shift cable and while im in there i was gonna replace all the bellows and maybe even the gimbal bearing and seals just becaus im in there and who knows when or if they ever were replaced. but any ideas what part i need to buy to fix this leak. attached is a pic of the leak.

Ayuh,..... When ya get it apart, hopefully, you'll find the problem,.....
It could be the bellows, or corrosion through the casting, or if the transom wood is rotten,, that could also be the problem,....

Not enough detail in the picture to tell,....

Took the outdrive off and there was lots of water in the gimbal area with lots of calcium buid up and rust on knuckles so im assuming this has been leaking for a while. I am replacing the gimbal bearing and seal obviously along with all gaskets, bellows water inlet hose and o-rings. While im in there im changing out the shift cable.If anyone thinks i should do anything else then let me know.
Ok so that all being said do you think the gasket or bellows was the cause of the water leaking in from the bottom transom plate drain hole? Or do you think i have a rotten transom? I took a hammer and tapped all around and got solid spring back from the taps so dont sound like any dead spots. But the only way that i can tell in transom is rotted is to remove motor and look behind transom plate from inside. And I REALLY dont want to do that just to find out its fine. Any suggestions? Also there is a very very tiny pin hole at bottom corner of the part of the outdrive that is attached to the transom it self is that normal or if not can i repair that with some form of epoxy from the outside without removing it. Because i again might need to remove engine to do that.
pics coming

Still leaking but really narrowed it down.
Ok so what I've done so far.
New
* bellows
* Lower Shift Cable
* tore apart entire stern drive replaced all seals and gaskets
* pretty sure I did all seals and gaskets on transom assembly
* new gimble bearing and seal
* removed old caulking and replaced around transome assembly

Think that's it and still leaks just as bad as before. Transom is a little soft only bottom right corner. Just on edge of assembly hole. If I SQUEEZE my hand down there i can feel its soft on inside edge but ita still farely strong only a inch or two in from edge. but there is no way itscoming from there. With the new 3m marine adhesive 5200 that **** isn't letting anything in even of transome was rotted badly not at least the first dip to test at ramp.

So here is where I'm at leaks just as bad as before which is a steady stream through hole not a small drip. Can't be from any of the things I replaced. Can't be transom (at least te outside edge). I found out that it is leaking just about where the exhaust bellow opening on transome. I found this out by slowly putting it in inch by inch and checking for leaks. It just started dripping not pouring yet but dripping at that point. Is there a gasket between outer transome assembly and how the exhaust meets up inside boat and is there a way for water to leak there.

I found out that it is leaking just about where the exhaust bellow opening on transome. I found this out by slowly putting it in inch by inch and checking for leaks. It just started dripping not pouring yet but dripping at that point. Is there a gasket between outer transome assembly and how the exhaust meets up inside boat and is there a way for water to leak there.

Click to expand...

Ayuh,.... There's an o-ring gasket there,...... 'n, if the shutters fell down into the y-pipe, the bits can wear a hole through the casting,....

The exhaust Y pipe is bolted to the transom mount on the inside behind the engine. There is a o ring seal between the pipe & transom mount. It’s possible that it is leaking there from corrosion between the pipe & transom mount. Unfortunately it takes pulling the engine to fix. That’s what is such a pain about I/Os. Leaks at the transom are a real headache. Y pipe, steering shaft etc all can leak like that.

And BTW there should not be any sealer around the transom mount; the seal for it is inside; if someone put sealer on the outside then there’s been a leak for a while & they tried to stop it that way, & it never works!

Soooooo after pulling motor and then the exhaust pipe and seeing one of the bolt flanges corroded I'm pretty sure that was it. But if it leaks again still I'm gonna cry. I'll keep you updated.

I got it welded and new hole drilled. Put it back on torqued to 50lbs. Really didn't feel to tight but left it at 50lbs. New oring seal and gasket sealant before seal on transom assembly flange , on seal and on exhaust flange. It's still leaking just half as much. Did I over tighten it or do I need to tighten it more. I do have the 1990 omc so I might be wrong but I believe on this year I csb go tighter due to having helocoils on this year. Correct me if I'm wrong

Ok so half the issue was the exhaust pipe obviously but I found under very close inspection a pin hole on the bottom corner of transom assembly. Wasn't sure it was leaking there till I had my daughter blow compressed air through it and I could see air flow from inside so if air is getting through water obviously is. So I think I finally narrowed down the last leak. Instead of buying a hole new/used assembly I'm just gonna use a dremel out the hole a little bigger and scuff it up then use JB Marine Weld to fill the hole and feather it out on outside the after that cures cover that with 3m Marine adhesive sealant 5200. That really should take care of it for as long as I own it. And if the 5200 ever gets compromised I'll just reapply or if need be buy the assembly then. I'll keep you all updated.

In these pics I first dremeled out the pin hole very slightly so I could push some Jb marine weld through the hole and then cover outside. Let that curw for a day and the I added a layer of the 3m marine adhesive 5200 (fast dry version) should be ready to get wet in 7 hours for hopefully the final leak test

Finally No more leaks. So to recap, there is two faults, one pinhole in the bottom right corner of the transom assembly. And a broken nut on the bottom right side of the exhaust flange, both contributed to the leak. It did have a small leak when I bought the boat which Was originally probably the pen hole. I just wanted to make sure I came back and gave the final outcome. Too many time these threads get started and the OG poster never gets back after they fix it. The whole purpose of these forums are not only to get help for yourself but to help the next person who might benefit from you trials and errors. God bless you all.

I have a leak from the same area you described. Was told it was probably the gasket on the exhaust horn where it bolts up to the transom. This means pulling the engine which I know you said you did. Mine is the four cylinder 3.0 Chevy engine. How big a job time wise is this and is the gasket readily available.

I have a leak as well in my 1990 Cobra 7.5 liter 460 CI engine and I am just starting to tear off the leg to examine all the parts and seals but your postings are definitely helpful as it gives me some ideas to look for other sources of the leak. Hopefully I won't have to pull the engine but if I do I have the equipment to do so. Too bad OMC didn't engineer a little more room between the engine and the transom. I keep you posted.