40hp Merc water in top cylinder

[dfrants]

just got a 1974 40hp Merc. she stalls and dies at idle. checked the plugs and the top one has a milkly residue on the end. thinking water is entering and mixing with gas somewhere. its not from the gas tank...made sure of that. it has 125lbs of compression. where is the mostly likely place for water to enter on a motor of this age?

 

[racerone]

From leaking exhaust cover gaskets or lower crankshaft seals.

 

[Texasmark]

Or, for an engine that age, especially if operated in salt water, pitting of the cylinder wall caused by corrosion, allowing block cooling water to enter the combustion chamber. I had that problem on a 22 hp Scott Attwater years ago.