I've seen this many times. It's time to change the exhaust risers, Bob. Make
sure you use OEM gaskets too. Some of the aftermarket stuff is garbage.
JIMinFL

"bob" wrote in message
...


bob wrote:

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

Spun motor with plugs out to blow water out of cylinder. Pulled block
drains to drain
water. Pulled intake manifold and head. The intake manifold shows some
internal rust
and the runner going to #5 cylinder shows the most. Cannot see any crack.
With the
head still attached, looking into the intake port of #5 can see red rusty
water sitting
on top of the valve. Pullled head and there was about a cup of water on
top of piston
5 and 7. Could not see any evidence of water leaking from intake gaskets
or head
gaskets.

Will look for place to test intake manifold today (lots of places test
heads) and get
both tested for leaks. Hope to find something cracked but if not, can a
leaking intake
manifold gasket leak into cylinder #5 only? I will check again but I
don't think there
is a water port close to the intake for #5 ...

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