1985 75HP Merc eating top piston

[Kawigamog]

At short burst of full to high speed aluminum chips caused spark plug to fail - once removed engine would run fine until short burst at high speed again - top cylinder only - new piston last fall - visable damage on raised part of piston - afraid to run engine at high speed again - why only top piston? if solid state ignition problem why only top cylinder? problem with crankshaft -spun- no visable damage to lower unit any suggestions

 

[rodbolt]

Re: 1985 75HP Merc eating top piston

its either lean or hot. some of the blocks had steam bubble issues so we located the tell tale to the top of the block, check your ign timing at WOT, not at cranking. check your fuel delivery system,not just carbs.<br /> something is creating heat in the combustion chamber that is leading to an uncontroled burn of the fuel mix. also known as detonation. as you can see it can actually eat pistons.<br />probably ate the first one as well.

 

[JB]

Re: 1985 75HP Merc eating top piston

Merc Trouble