250 hp 350 engine with hydro lock on cold start

[Griff 4]

Hi all. My starboard engine has been showing a hydro lock while starting when cold. I had suspected exhaust manifolds and risers, so changed them. It seems to only be a small amount of water getting atop no. 1 cylinder piston only. Has anyone seen this problem before? I am sure open to suggestions! Griff

 

[DWABoat]

Did you see evidence of water leaking in the exhaust port when you removed the manifold?

May be a head gasket.

 

[scoflaw]

Heads can rust through. Vortec heads have a thin casting

 

[Griff 4]

Engine is seawater cooled. General consensus seems to point towards a possible head gasket failure. I am still checking a few things before tearing down. Thanks for your advice. Griff.

 

[Griff 4]

All apart now. Water inclusion in no.1 cylinder only. Could not see any head gasket smoking gun, but suspect that the intake manifold gasket was allowing water to creep into the no. 1 intake port on the cylinder head. Will clean up this mess and very carefully reassemble. Will report upon completion. Thanks for your expert advice. Griff.

 

[Griff 4]

Hi all. Thanks for your input. I was expecting to find a bad head gasket. But she purrs like a kitten now and the problem was the intake manifold gasket. Coolant was slightly leaking from atop the forward left side of the intake manifold. This allowed the coolant to creep along and enter the no. 1 intact tract. There was obvious rust trails showing the seawater getting past the intake valve and filling no. 1 cylinder. On the 250HP 350 carb engine, the view of the failure point is obscured by a large coolant hose and the gear oil monitor hose.