Manifold passes leak test - leaking when hot?

[PatrickBoyle]

Mercruiser 120. Standing water in cylinders after running. Exhaust channel in bottom of manifold is full of water when pulled off. Both the manifold and elbow pass the Acetone test. Good compression in all cylinders (some variation, but none below 125psi). Block cooling circuit has been pressure tested to around 18psi and held for about 15 minutes (lost maybe 1psi during the test).

I'm wondering what the chances are that the manifold has a hairline crack that opens up when the manifold gets hot. The thing is, theres a lot of water getting in when it's up to operating temp; enough to foul plugs and cause cylinders to miss below around 2000 RPM.. I can't see if being a head gasket considering compression is good and the water jackets hold pressure. Ideas?

 

[elkhunter338]

Re: Manifold passes leak test - leaking when hot?

with that much water leaking. Fill the manifold up and us a big propane torch to heat it up an see if the water runs out the exhaust or intake ports that would put water into the cylinders.
That sound like an awful big leak if it's missing below 2k.

 

[PatrickBoyle]

Re: Manifold passes leak test - leaking when hot?

Yeah this one's got me stumped. I've got a known good manifold I'm going to install next week, but I was thinking of just going ahead and replacing the head gasket while I'm there. The head bolts on the 120 are not torque to yield, correct? Can they safely be re-used?