Water in one cylinder on V8 Mercruiser. Pull the head?

[patrik01]

Been busy getting water out of one of the cylinders on my V8 Mercruiser. Manually cranked the engine over with a starter button I hooked up and I shot in air with a compressor through the spark plug hole and exhaust hole in the block (took off the manifold). Got most of the water out but when I leave it for a while (even next day) I still get more small spurts of water coming out. I did a compression test of all four cylinders on that side and the cylinder with water, only gets up to 100 psi so something is off (eg piston ring). Now my question:

Does that mean I have water leaking in from above the cylinders due to a broken head casket? I assumed the gasket between the manifold and elbow riser was the culprit. There was water in the manifold and I can see rust in the four exhaust ports even if only one cylinder seems to have an issue.

Should I assemble everything first and dry to burn any residual water once fuel and air fires up the engine? Or am I left with pulling the head?

 

[Bt Doctur]

if you already remove both manifolds, put muffs on drive, start engine to dry the cylinders, NO MORE THAN 25 SECONDS AT A TIME
If you never overheated it then I have my doubts on a gasket. Most water issues are leaking riser to manifold areas or a physical crack in manifold or riser

 

[flashback]

Put some earmuffs on your own ears and either pipe the intake water overboard or pull the garboard plug.

 

[patrik01]

Thanks. Drained water from block (only a few drops) and the other manifold that's still attached which looks ok and where I had no water from spark plug holes.

Been driving the boat around 5-6 hours per year the last 10 years and not had an overheating issue. Mainly low cruising speeds. Winterized with anti freeze every winter without a leak so far.

Bit confused how water could enter into just one cylinder from head gasket. Is head gasket the only thing that stops water from the cooling channels through the block?

The low-ish compression in one cylinder could be a previous issue I never noticed.

The exhaust holes in the block after taking off the manifold all look a bit rusty so feels like the manifold is the source.

But again where the small spurts of water in only cylinder is coming from is odd. Unless it's hard to fully expel all the water with cranking and compressed air.

Maybe running the engine once manifold is back on and hook up the garden hose to mufflers is the only way to fully clear it as you suggested.

 

[Scott Danforth]

Probably not the head gasket. Most likely exhaust manifold/riser leak

 

[ScottinAZ]

Probably not the head gasket. Most likely exhaust manifold/riser leak

I would say either manifold or cracked head.