Mercury Mariner 3L EFI 1997 bogs down after warm

dreamcruise

Recruit
Joined
Aug 3, 2018
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5
Engine runs well in the morning but shut it down and fish for a while, then restart to go home and it won't run over 3k. Raise the prop almost out of the water, move passengers to the bow and sometimes you can get her going but most times not. I checked compression, re-gaped plugs,removed each coil and looked for burn tracks. Used an inductive tach on each Cyl coil and all the same.an idle. The plugs were a bit oily looking but not fouled. Is this normal for a 2 stroke oil injected engine? Does this engine have a knock sensor? Couldn't see it on the schematic. A friends mechanic said it might be the O2 sensor. REALLY!
 
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