Water in #8 piston on 2001 5.7 L Mercruiser

[Daycation]

I have a 2001 Sea Ray Sundancer 5.7 liter Mercruiser with water only in the #8 cylinder. Exhaust manifold and rods are not leaking. Could the water be coming in from the throttle body? Or any other suggestions?

 

[CharlieB]

Re: Water in #8 piston on 2001 5.7 L Mercruiser

How do you know the exhaust manifold is not corroded internally and leaking into #8 exhaust port? Have you taken it off, looked, and had the manifold pressure tested? This is the most likely cause.

Second most likely cause is a leaky head gasket. A cyl leak down test may be useful, lower readings on #8 can be cause to remove the head.

 

[TilliamWe]

Re: Water in #8 piston on 2001 5.7 L Mercruiser

How do you know the exhaust manifold is not corroded internally and leaking into #8 exhaust port? Have you taken it off, looked, and had the manifold pressure tested? This is the most likely cause.

Second most likely cause is a leaky head gasket. A cyl leak down test may be useful, lower readings on #8 can be cause to remove the head.

I agree whole heartedly. Except the second most likely thing is the exhaust riser. The third most likely is the exhaust manifold. And the 4th most likely is the exhaust riser. Then maybe the head gasket (SBCs don't just blow headgaskets for no reason, and can withstand some pretty high temps)

 

[Daycation]

Re: Water in #8 piston on 2001 5.7 L Mercruiser

How do you know the exhaust manifold is not corroded internally and leaking into #8 exhaust port? Have you taken it off, looked, and had the manifold pressure tested? This is the most likely cause.

Second most likely cause is a leaky head gasket. A cyl leak down test may be useful, lower readings on #8 can be cause to remove the head.

Thanks for all of your responses!

I removed the bolts from the exhaust manifold, put studs in, slid it back about 3 inches and applied water. No water came out of the exhaust manifold. There is no water in my oil, but I did notice my throttle body is corroded, with water dripping on it through the engine cover. Could the water possibly come in through the throttle body?

 

[Daycation]

Re: Water in #8 piston on 2001 5.7 L Mercruiser

Bump