bob wrote:

How do you trouble shoot the cause? Intake gasket vs head gasket vs crack
somewhere? Done some searching in this group and hoping exhaust manifold may
be the problem but don't want to tear it apart if I can do some diagnostics
first.

I posted this last summer but problem appears to be back. This is a
Mercrusiser (Chevy 350 block in a 1992 boat) that I overheated due to raw water

pump failing (now have a buzzer installed). On this occasion, I launched and
drove slow for 1/2 mile or so and then pulled a skier 1 mile or so (3200rpm or
so) and noticed temp gauge pegged so stopped.

At that time,I pulled heads, all pistons pretty much the same black top, had
heads
milled and valve job (motor has ~1200 hours on it). Cleaned block and intake
and put back together. Not sure I wasn't still getting some water in oil after

this as I could see some condensation under oil filler cap and either lots of
blow by or steam coming out of the valve cover vents but it seemed to get
better as the motor warmed up. Assumed it was condensation. Changed oil today
and
looks like chocolate milk...

Without any good diagnostic test I guess I will just start to pull apart and
see if I can find anything. Tried to do this last year but the gaskets tear
and can't really tell if it was leaking or not. I'd love to just change the
exhaust manifold or intake gaskets if that is all that is wrong but if I have
to tear down to the heads again, I will probably just go for a complete
rebuilld and have
everything checked. I really don't think it needs it as there was no ridge
ring that I could see or feel.

Thanks for any and all advice.
Bobby

After searching the web some I more found that cracked exhaust manifold can let
water in through exhaust valves and this will cause a hydro lock. After thinking
about it, after sitting for a few minutes and hitting the starter, the motor spun
and hit somehthing hard, stopping the starter. Tried again and it started.

I pulled the exhause manifold on left side (port I think) and saw rust in #7
exhaust port (the motor is tilted up 10 degrees or so making this the lowest
point). Did compression check and water blew out of spark plug #5. All cylinders
checked 175 - 185psi. I cannot see any cracks in the exhaust manifold. Plugged
holes with duct tape and filled the water jacket with water but the inside stayed
dry. The manifold was very easy to seperate from the riser so maybe it was leaking
but cannot see any signs based on gasket and rust tracks. I will try to get the
manifold checked today but not sure if it really can be done.

I know water enteres #5 cylinder and understand it can come from exhaust.

* Would the intake gasket possibly cause this?
* Do the intake manifolds sometimes crack and cause this?
* Would a head crack cause this and still show 175psi on a compression check?

I hope to find a crack in the exhaust manifold but if not, I am tempted to put new
gaskets in the exhaust riser and see what happens.

Again, any thoughts or comments welcome.
Bobby
bbusselman at hotmail dot com