Reply To: Mercury Mark 55E

[jeff-register]

It may need crankcase seals, or mating surfaces leaking making it run lean, and or low compression Do a compression test & post. Have you tested the oil & gearcase? Friction will load a motor. On the top of the cylinderblock it has a test plug for water. Put a barbed fitting for a 1/4″ pee hole to be sure the cooling water is getting to the top cylinder. When running squeeze the primer bulb. Should be soft when running & hard when stopped.