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    Leaking water at base gasket

    Just put together my mercury 3.9 after a complete rebuild. When its running there is a little water in the lower cowel. Looks like it is coming from the base gasket. I originally used permatex aviation form-a-gasket on both side of the gasket let it sit for 3 days before I started the motor ...
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    Mercury 3.9 fuel pump rebuild

    Thats what I pulled out , will just put the same back in. Thank you for the info
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    Mercury 3.9 fuel pump rebuild

    Serial# 1782634
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    Mercury 3.9 fuel pump rebuild

    Currently chasing down a fuel issue with my mercury 3.9. When rebuilding my fuel pump the new rebuild kit has an extra gasket (the one at the bottom of the picture that’s solid with the two small holes in the middle) that wasn’t on the pump when I disassembled it. Does anyone know where this...
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    Mercury 3.9hp compression range

    I ended up taking apart the powerhead to better inspect the piston and cylinder. Found all three stuck rings and pretty bad scoring on the piston from about the bottom ring to the bottom of the piston. Cylinder walls looked fine. Ran my nail around it and never caught and groves or scratches.
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    Mercury 3.9hp compression range

    ok I checked the things you recommended. 1. Yes the spark will jump a 5/16 gap. 2. Added 8 drops of fuel directly to piston through spark plug hole. Tried to start it by pulling 5-6 times on pull cord. Motor never tried to start at all, it looked like maybe a small amount of smoke or vapor...
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    Mercury 3.9hp compression range

    Will do this weekend when I get home. Thank you for the advice. I’ll report back later
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    Mercury 3.9hp compression range

    I’ll have to check the spark at 5/16 when i get home. It has bright spark on plug set to 0.030. I looked through the bypass yesterday. Some carbon build up on the top. But side looks good no discoloration,some light vertical lines on the side but nothing deep. Rings looked good, nice and bright...
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    Mercury 3.9hp compression range

    Hello. Trying to diagnose a no start on a 3.9hp outboard. Was getting 60psi off a cold motor compression test. Does anyone know the range this motor is supposed to be at. Manual just says it’s supposed to be within a certain range of the other cylinders, but this is a single cylinder motor so i...
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