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water leaking in bilge above y pipe only when motor is off
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Author:  yoid [ Wed Jan 27, 2016 12:11 am ]
Post subject:  water leaking in bilge above y pipe only when motor is off
hello everyone, i have a 1992 195 sundowner 4.3 omc cobra and i have water leaking in my boat only when the motor is turned off, if i start motor the leaking stops. it seems like its coming from above the y pipe. i put the boat back on trailer and slowly lowered it into the water until it started to leak again then slowly took it back out and it starts when the waterline is about 3 inches or so below the omc bagde on the back.
Author:  alex8q4 [ Wed Jan 27, 2016 8:17 am ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
Is this new?

Sounds like you have a leak in your drive shaft bellows.
Author:  rpengr [ Wed Jan 27, 2016 8:23 am ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
I once had that problem on my 1987 4.3 Cobra. It was aluminum corrosion of the y-pipe at the gasket seal. The reason that the leak stopped when the engine is running is that while running, exhaust pressure kept the water out.

If the drive shaft bellows is leaking, then it will still leak with the engine running...although it might get slung about so you are not seeing it.

I had to pull the engine and replace the y-pipe. :(

Take a very close look with your phone camera or mirror at the top of the y-pipe to see if the water is coming from the gasket seam where the y-pipe bolts to the transom bracket.

Once the Y-Pipe is removed, it might be repairable by welding and machining. Or it can be replaced, but it is likely that the OMC y-pipe is not available. I had used a new Volvo Y-pipe, but I had to modify it slightly by denting in the pipe where the shift cable sheath came in contact with it. (the OMC pipe has a notch there. the Volvo does not). I also had to make an adapter plate because the shape of the gasket surface is different (although the hole pattern is the same). The adapter plate should be made from Aluminum, at least 1/8" thick. I made the mistake of making a SST plate the first time I did this repair. The SST plate caused galvanic corrosion of the aluminum surface, so after a few years it started leaking again. So I had to pull the engine again and machine the gasket surface and make a new aluminum adapter plate.

Ray
Author:  yoid [ Wed Jan 27, 2016 10:05 am ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
This weekend I will try to have a look on the top of y pipe and around the gasket. Pretty tight in and around there. Do you have to pull the motor to change y pipe, and is it hard to do? Thanks for your advise I'm new to I/0 boats.
Author:  yoid [ Wed Jan 27, 2016 10:10 am ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
i was thinking of putting water in the bilge just enough to cover bottom of y pipe and chr k to see if I leaks out the back. If it doesn't then jack the front up a bit at a time to make the water move up the transom wall to see where it comes out. Would this help in seeing if it's the bellows?
Author:  rpengr [ Wed Jan 27, 2016 10:22 am ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
yoid wrote:
i was thinking of putting water in the bilge just enough to cover bottom of y pipe and chr k to see if I leaks out the back. If it doesn't then jack the front up a bit at a time to make the water move up the transom wall to see where it comes out. Would this help in seeing if it's the bellows?

That would help to determine if the leak is down low at the y-pipe, or it could also be the seal around the transom bracket (the transom bracket to transom outside surface). However, you do not want to put in enough water to test the drive shaft bellows. If you did, you would be soaking your u-joints, and you would have already submerged your starter. Do not put in enough water to submerge the starter.

Others on this forum have written about leaking seal between transom bracket and transom. However, this leak would not stop because the engine is running. Only the y-pipe fits that symptom.

Yes, you do need to pull the engine to change the y-pipe. It's quite a job, but it can be done as a DIY job if you have access to an overhead crane.
Author:  signalstan [ Wed Jan 27, 2016 7:09 pm ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
I used to have a 1992 bayliner with a merc. 4.3 v6 the merc y-pipe has flapper valves in it to prevent water from backing up into the engine both of those valves got loose in the y-pipe then rattled around in the bottem of the y-pipe untill the made holes in the pipe causing it to leak into the bilge. merc had a defect that caused this. the replacement part was redesigned. I am not sure if volvo ever had this issue
Author:  yoid [ Thu Feb 04, 2016 11:02 pm ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
So i flooded the bilge (not passed the starter) and water started coming out the back exhaust .Not completely happy i did some more looking at the video and pic i took of the water coming in as well as the water line in the bilge. I then stuck a very bright led light in the exhaust and noticed a line of light glowing off the transom. I'm thinking now that the gasket around the exhaust maybe gone. I used a telescopic light to see the top two bolts of the exhaust aswell as a mirror to see the bottom, the pipe looks corroded, but not rusted through as i have to take the engine out to get to the gasket i will prob change the pipe anyway. Just looking for a reasonable priced y pipe omc#986117 and volvo n#3858873 if anyone has any idea that would be great.
Author:  yoid [ Thu Feb 04, 2016 11:03 pm ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
how do we post video clips to this forum?
Author:  rpengr [ Fri Feb 05, 2016 8:54 am ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
yoid wrote:
how do we post video clips to this forum?

Probably best to post to youtube and then place a link here.

I once did a weld repair on an OMC cobra Y-pipe (at the gasket surface), and re-machined the surface flat. Something to consider.
Author:  yoid [ Thu Feb 18, 2016 11:11 pm ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
Well I got the motor out today and found a hole in the rear of the y pipe and the mounting bolt eye holes on the bottom were all corroded so they looked like the letter c also someone had been in there already the gasket looked torn on the bottom (unless it torn when I removed it) but don't think so they had put some other sort of sealent in as well. Hopefully the part is in tomorrow and can put it all back together. Keep you posted
Author:  yoid [ Wed Mar 02, 2016 8:39 pm ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
Put the new y pipe in and no leaks everything is good. I would like to thank you all for your advise and support. thanks agin
Author:  rpengr [ Thu Mar 03, 2016 9:01 am ]
Post subject:  Re: water leaking in bilge above y pipe only when motor is o
Image

Glad to hear it. Maybe I'm too late to mention it, but this would be a great place to use Tef-Gel on the gasket surfaces and hardware to prevent corrosion.

Ray
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