The boat is a 1992 Malibu with the Mercruiser Magnum Skier (Chevy 350 block)
and the hour meter says 996, if that makes a difference. The raw water pump
went out and I drove it maybe 1/2 mile before noticing the temp was maxed out
at 212. Stopped and let it cool some and idled back to the ramp in 3 segments
(ran till temp went back to 200, stopped and floated 20 minutes or so and did
it 2 more times).

Checked compression and ran 175 -180 across all 8 cylinders. I pulled the
intake manifold hoping to find evidence of it leaking, but could not tell as
the gasket tore up as I pulled it off. The intake was still full of water, so
the motor didn't run dry (the engine water pump still circulates this water
through the engine even if the fresh/cool water has stopped coming in).

Questions, when an engine overheats and water gets into the oil, what is the
most likely cause and is there a way to test? Since the compression tested OK,
I was hoping to find a bad intake gasket, but cannot tell. Does the good
compression point more towards a head gasket than a crack in the head (assuming
the combustion chamber is the hottest and would be the first to crack). Also,
does overheating tend to crack blocks? Is there some path that lets water
(steam) into the crankcase without there really being a serious problem?

Any advice or shared experience appreciated.

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