Water in bilge from transom

[Big Boat Bay Buster]

1987 Mercruiser 260, Alpha 1 gen 1. My bilge is usually bone dry. Well not any more. No leaks from the engine. Traced the leak to the lower part of the transom.The area where the hydraulic lines go through. I figure either its the main transom seal,the housing for the hydraulic lines or the Y pipe.
What I'm asking is what is a more common place for a leak and the best way to test for it. The bellows are all good and I have eliminated the stendrive as a source for the leak .I am in salt water, but trailer and flush after each use. Can a Y pipe corrode to a point that it leaks?
Thanks, Chris

 

[Don S]

Re: Water in bilge from transom

There is no such thing as a common place for them to leak. Yes, the Y pipe can corrode. there is also the manifold that the trim hoses attach to that corrode, crack and can leak water, the transom could be soft allowing water in. Hard to say exactly what is leaking. You just have to determine what is causing YOUR leak.

 

[Bifflefan]

Re: Water in bilge from transom

A few things to think about.
In my boat, the PO had poorly intalled a live well. The thru-hull for the drain had no nut. this let water in and over time caused the bottom of the transom to get soft and let it flex. this caused the exhaust to come loose and let in more water which in turn made things worse and worse.
Im not saying your is this bad but, do what ever is nessarry to repair it now. Dont just fix half the problem. when you find the leak and stop it, make sure you keep looking for any damage already caused by it and fix it while its small.
A week off the water this year can save months off next year.

Take a read at what im dealing with.

84 21' 470 Overhaul begins. (with pics)

 

[Big Boat Bay Buster]

Re: Water in bilge from transom

Its still not clear where the water is leaking from. Long story short, pulled the engine and removed the Y pipe. Still no smoking gun.Other than the fact that the pipe has a symetrical bolt pattern and the transom does not, it doesn't appear to be leaking. There is some rotten wood on the transom at the bottom, but I'm not sure if its from the inside area being wet or from outside water getting in. Otherwise the transom is solid. The outside of the boat around the transom looks good and feels solid.
So whats my next step?
Pull the transom plates apart?
Great way to spend the holiday weekend!!
Chris

 

[Bt Doctur]

Re: Water in bilge from transom

Double check the Y pipe again, especially the bottom where the idle relief ports are.
Also check where the trim wires go thru.the water connection tube.

 

[NHGuy]

Re: Water in bilge from transom

Hey I'm a little late with this approach but maybe you can use a modified version. I have heard of some folks putting water in the bilge while the boat is out of the water. Then watch the outside of the boat for water exiting.
I wish you luck in your diagnosis.

 

[Don S]

Re: Water in bilge from transom

Put the Y pipe back on, and put the drive back on (new gasket kit for the drive) then put the boat in the water and look for the leak. With the engine out of the way, they are usually easy to find.

 

[Bifflefan]

Re: Water in bilge from transom

That is a dead ringer for my leak damage.
If you have no other penatrations throught the transom, id say the exhaust has been leaking water, of the gimble houseing gasket is bad.
Id remove the gimble housing and replace that gasket as you have it almost out anyway. It cost 8 dollars and is good insurance. While you have it out, got yourself some "Git-rot" (avail at West Marine or where ever) put tha in the bad wood in the bottom, even if its not soft right now. Again good insurance. then clean the exhaust mating surfaces and install new gaskets, (Again about 5 dollars) as you put it back together. there is an o-ring gasket that goes in the joint between the Y pipe and the gimble housing. Use red lock tite on the bolts and you should be fine. Also looks like you are going to need the 2 lower bolts for the gimble housing. these are $48.00 and come in a set with new anodes.

Looks like you have caught yours in time as to not have major damage like mine.

From the looks id say where the Y pipe bolts to the gimble housing was the leak and you should be able to fix this with little difficulty.
Like I said im dong the same repairs right now so PM me if you have any questions i may be able to help with.

 

[Fishermark]

Re: Water in bilge from transom

Other than the fact that the pipe has a symetrical bolt pattern and the transom does not, it doesn't appear to be leaking.

Surprisingly enough - Mercruiser says that's an acceptable setup. (I know because I found the same on mine). Your transom assembly is designed for the single pipe and you have a Y pipe. Seems they allow the boat manufacturers to use whichever one they have available.

There is some rotten wood on the transom at the bottom, but I'm not sure if its from the inside area being wet or from outside water getting in. Otherwise the transom is solid.

I would suggest drilling some exploratory holes from the inside around the bottom of your transom.... I bet wet wood comes out instead of sawdust. That means transom repair work.

I believe you will also find those bottom two bolts are corroded away. They are an aluminum alloy of some sort and the water will eat them up.

Did you pull the manifold off for the hoses? Who knows? Maybe you will get lucky and simply need to replace the gasket.... but I suspect not. Sorry.

 

[Big Boat Bay Buster]

Re: Water in bilge from transom

Problem solved--shift cable boot had a tear in it. I missed it on the initial inspection. The tear was on the inside, facing the universal bellows. Bilge is now bone dry!! Its a pleasure knowing that salt water in not splashing around on the bottom of my rebuilt engine.
I know I'm bringing up an old post, but I believe its important to post my fix to my question for others who may have a similar problem.
Chris