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2002 Mercury 90 hole in piston

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wjefcoat

New member
I recently purchased a boat with an 02 mercury 90. It would not run right so i cleaned the carbs, checked the compression ( it was fine on all 3), took it back to the water and it ran better but not great. I took the plugs back out and had no conpression on the bottom cylinder. When I took the motor down, the piston is burnt on the exhaust side. Any suggestions.
 
lean lean lean to burn a hole through the piston...was that carb maybe starved of fuel? Im not an outboard expert but thats 99.9% of the case in all other small engines which i am very good at...
 
Thak both of you for the info. My piston actually looks like the pic titled "Burnt Out Blow Hole" time ten. What makes it run lean, I'm a diesel mechanic so carbs, especially two-strokes are not my thing.
 
wjefcoat said:
Thak both of you for the info. My piston actually looks like the pic titled "Burnt Out Blow Hole" time ten. What makes it run lean, I'm a diesel mechanic so carbs, especially two-strokes are not my thing.
Click to expand...
More than likely the lower carb main jet is plugged, or the float is stuck closed (unlikely). Consider your engine as 3 separate engines on the same crank. If 1 cyl doesn't get gas it doesn't get oil, but still moves at speed. Anytime there is a lack of performance stop and fix it.
 
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