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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11052
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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1991 60 hp evenrude ,keeps burning top piston ,engine is not

Customer Question

1991 60 hp evenrude ,keeps burning top piston ,engine is not hot,smokes some ?? When running .placing third piston now.
Any help ?
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

Have you verified you have the correct jet in the top carb? Ids the jet in the bottom of the carb spotless clean? Have you verified the timing and top dead center?

Customer: replied 1 year ago.
Should be factory jets in carb? Size I will haft to check.What is the correct size? To best of my knowledge time is correct ?? I'm an ex outboad mechanic ,have rebuilt dozens of engines,with minimum issues .Never had an internal issue ,All ways the first time.Third time blows my mind.after each rebuild the engine has been in storage for extended periods of time but use some also. owner is in military often deployed. But over all low hours between issues.
Thanks Roger
Expert:  Tan replied 1 year ago.

The engine sitting allot could be an issue and the high speed could potentially be partially clogged. If fuel is left in the carb it will cause issues especially with the high speed jet as it is in the bottom of the carburetor. Poor quality fuel. Ethanol in the fuel causing a fuel restriction.

The jet is a 44D

Customer: replied 1 year ago.
Ok ,I don't mean to sound stupid ,have the carb apart I see not jet ,that could be remove or changed.carbs look clean ,but will give them them a good cleaning.the other issues you mention are common things to check .maybe I was think omc may have had an issue with model ?
Thanks Roger
Expert:  Tan replied 1 year ago.

# ***** is the jet and it does screw out of the bowl. If it is dirty at all it will lean out the cylinder and burn piston. If you have the old piston can you post a pic?