I have a 90 60 hp mercury outboard with aluminum fouling on the #1 cylinder?

Question

I was at WOT when lost the 1st cylinder. Does this require an engine rebuild or is there another fix? Any ideas for the cause?

Answer 1

The cause was from overheating,either by lack of water or too lean fuel mixture.In either case you will need to rebuild the engine if you want to get the best from it.

  Since there is spaling on the cylinder wall chances are the rings have seized and you have little or no compression on that cylinder.

  When you rebuild you may only need to remove the aluminium with mercuric acid but if the walls are scored then you will need to bore out the cylinder.

You don't have to oversize both cylinders unless both are scored.I do recommend that you re ring and reseal the whole engine.

  Before you restart the engine first establish the cause of the overheating problem.

  35 years as a marine tec.

Answer 2

Piston slap.. Top end bearing faulty or worn. Would recommend that the main end is checked also. If its just a small amount of build up on the bore about halfway down from the piston skirt then its surely a worn out top end. replace piston and hone out bore. Other possible cause. under size piston used on rebuild or piston placed wrong way around in the cylinder. Pistons have a marking on top that faces forward.