Mystery leak

[stonyloam]

Ok took the boat out (87 4winn, 470, Alpha1) noticed I was getting some water in the bilge. Dried it out, thinking maybe bellows, but no water was coming in. Started the engine (in neutral), slow drip appeared at bottom of transom plate, can't see where it is coming from. Increased RPM, leak increased. Put the boat in lift, so that bellows were out of the water, tried again, same results. It is not the bellows, nor the seawater hose in the boat, only leaks when running. Could I have messed up when installing the outdrive gaskets, May just have to pull the outdrive to see what is going on. Any thoughts would be appreciated.

 

[Big Boat Bay Buster]

Re: Mystery leak

Interesting, I have an 87 Four Winns horizon 21' with the same leak. I just replaced the main seal, Y pipe seal and gasket for the trim lines. I still have the leak. I eliminated the bellows as a source for the leak.
You need to get your head in the back of the engine and see where its comming in from. You may need to pull the drive to double check its not from there.
Sorry I don't have a better answer
Chris

 

[Rscardina]

Re: Mystery leak

fresh or raw water cooled?... heat exchanger or no?...

if its dripping more when you throttle..and the water pump is mechanical then it would appear that its something in the water distrubution..

as suggested already..I would get my head back in there and see if you have a hose leaking or something of that nature

 

[stonyloam]

Re: Mystery leak

Closed cooling, and it is a fresh water leak. I have looked back there as best I can (Head too big, and neck too short). Can't see where it is coming from. I did install a new shutter, so maybe I did stress the exhaust pipe putting it back together, could have caused a leak in the gimbal housing seal. It is even more of a mystery now, because it has stopped leaking, just a few drops on a 10 mile mostly WOT run. Going to keep an eye on it for now. Thanks for the ideas.

 

[NHGuy]

Re: Mystery leak

This is only a guess but maybe you do have a bellows leak or bellhousing leak allowing water into the bellows. In that case the water may be coming in when the motor spins throwing it up against the gimbal bearing where a little at a time gets through.
Might be worth pulling the drive for a look.

 

[stonyloam]

Re: Mystery leak

This is only a guess but maybe you do have a bellows leak or bellhousing leak allowing water into the bellows. In that case the water may be coming in when the motor spins throwing it up against the gimbal bearing where a little at a time gets through.
Might be worth pulling the drive for a look.

I don,t think it is coming in around the driveshaft. Since it has pretty much stopped now, I may leave well enough alone. If it starts up again will have to pull the drive.