Water accumulating on spark plug

[Robert]

77 Johnson 15 hp, 15E77M,
Engine starts and runs fine except! Starts out fine under load, shortly it begins to labor and hesitate, removed plugs, top is fine, lower plug has water accumulated in recess around electrode and some on tip. Clean the plug and it will water foul again in just moments. I'm getting water into the crankcase (from the water pump) indicating a gasket, hole in plate etc. Where should I start to find water intrusion point? What is the most likely culprit? Should I just disassemble and replace all gaskets? What area is the most likely to fail? As you can probably tell, I want to eliminate the easiest to repair first. Thanks for any help.

[boats.net]

Probably need to remove head and check head gasket and if any holes are corroded through head.

[mr880]

Water on spark plug

I had a similar problem with an early 70's 18 Evinrude. I found that the end of one of the cylinders had been 'eaten away' by electrolysis. The rough surface at the end of the cylinder right where the head gasket makes contact was worn away enough to allow water from the cooling jacket in small amounts to enter and constantly foul the plugs. This may or may not be it but you might want to pull the head and take a look at that surface. I've never seen this happen before or after. It was a surprise. If this turns out to be the condition the block is probably scrap. I don't think there is enough metal to do a surface grind.