Stuck Valve and water in oil

[AIM]

This is an update of my "sudden loss of power"/ "3 oil change" postings.

I went back to the boat yesterday and pressure tested the jacketed exhaust system. It held 7 PSI for nearly 20 minutes so I'm assuming I can rule out a hole in the exhaust pipe as a source of the water.

A friend with a lot more experience than me joined me to take a look. We did another compression test on cylinder #1 (closest the flywheel) and it continued to have zero PSI.

His diagnosis is a stuck intake or exhaust valve which seems to fit what I've read on several of the postings. Where he differs however, is that he says the stuck valve can actually be the cause of the water entering the engine, not just the result of it. He feels that the vacuum within the combustion part of the engine is strong enough that if a valve becomes stuck open it can draw water back in from where it exits the manifold.

Is this something that anyone has encountered? It seems to me that with this jacketed system where the water and gas don't actually mix until just before they exit the transom, that there is no place close enough for a vacuum to pull water back in.

His recommendation: Pull the carb, remove the fuel pump, take off the valve cover and I should be able to see something not looking right (broken spring or stem, maybe even just a piece of carbon jamming things up)

Any thoughts?

I used my topsider on the oil change tube again and was unable to get any more free water out of the engine which I'm thinking is a small piece of good news.

[ndutton]

I've never heard of a stuck valve drawing water in through the exhaust but I agree with everything else your friend said. Deal with the valve issue in #1.

You pressure tested the manifold, how about the rest of the cooling system?

[AIM]

Neil:

My pressure test didn't include the manifold.
I removed the H2O hose exiting the manifold and removed the H20 hose at the stern where it mixes with the exhaust. I wanted to make sure there wasn't a hole in the inner part of the jacketed exhaust

If I repeat this test but include the manifold, where would I seal up the engine side end of the loop

[ndutton]

My mistake. I read jacketed exhaust and because they're so rare immediately thought jacketed exhaust manifold. You can test the entire cooling system by removing the raw water discharge hose from the pump and seal it.