Gary Anderson

BT,
Log exhaust, second from rear. Unlikely to be reversion from a cracked riser.
Gary

blue thunder

I've never owned a boat with log manifolds. How far back does the water/exhaust gas mix? When ever I've had water problems from leaking exhaust it has been the center 2 cylinders 3,4,5,6 on either side. That was with center rise manifolds though and not being able to keep riser gaskets in.

Another question, are you getting milky oil? Leaking exhaust will drain into the crankcase through open exhaust valves when let sit for a few days. Have you ever serviced this exhaust?

BT

Gary Anderson

Log style enters at back (cylinder 8), that plug is fine, it's the one forward of 8 that looks clean.
No, on the milky oil. No signs of contamination at all.
I know what you mean about leaking risers with center rise, always the center 2 cylinders.
Looks like the exhaust is coming off.
Does everyone agree that with those symptoms & compression/leakdown numbers, I can rule out head gasket and crack in cylinder head?
Gary

blue thunder

If you have serviced the manifold in recent past and feel they are clear, I say you need to collect more facts before tearing into it. That of course depends some on how tough a job getting the manifold off will be. Mine are very difficult with engines in the boat. Generally if you are getting water from exhaust cracks it will be worse in the combustion chamber or above the valve after sitting some. After it sits, remove the suspect plug and while holding a paper towel in front of the plug hole, have someone crank the engine (kill switch out). If water flies out and wets the towel, you have to remove the exhaust. If it remains dry, I would run it until I have more facts. Hopefully those facts would not be a valve head coming off. Is this spark plug getting rusty too?

BT

Lmarth

Gary- This sounds like a tough one. If one plug looks like it's steam cleaned, you've got water getting in that cylinder. You said the manifold and block were pressure tested and passed. Did you pressure test the head? You could have a leaking head gasket or a cracked head. Once had steam coming out the exhaust. Couldn't find anything until I pulled the head. The engine was still warm. Saw a dark line in the combustion chamber between the intake and exhaust valves that was leaking water. Pulled those valves to find a crack between the seats. My experience is that a compression test won't show something like this. 15% leakdown isn't the greatest. Was the "steam cleaned" cylinder out of line with the other cylinders? This could be nothing at all or a problem in the making. How many hours since the motor was apart? Keep us posted. Lou