60 HP Mercury 2 stroke outboard has lean misfire

[V-Tech]

2001 Mercury 60HP 3 cylinder outboard has a lean misfire at idle and above. It idles very low and stalls. The misfiring cylinders do come to life if you briefly push in the choke (ignition key) while it is running. Yes, I know it does not have a true choke. I know the following about the engine at this time: Compression 115 psi all 3 cylinders. Fuel filter is new and clean. Spark plugs are new and clean. Float bowls are not plugged with varnish or jelly-like spoiled fuel- I have removed float bowl on dead cylinder to inspect-looked very clean. Fuel is fresh. Fuel is flowing freely to the carburetors.
After tinkering with it in order to learn what I do know to be good it ran normally for a little bit, then went back to the lean misfiring. What do you think I should check next?

 

[1nebel0]

Re: 60 HP Mercury 2 stroke outboard has lean misfire

You need to do a lync and sync first....check the timing second...check electrical being coils, stator. Are you sure you got the correct jets in the motor for what it calls for. I can't tell you how many motors I buy and the first thing I check for is the correct jetting per the manual. This is probably a long shot but you have to eliminate everything...Float bowl isn't the only thing that needs to be clean...one small blockage and you are lean on that cylinder...Figure out by pulling a wire which cylinder is causing the problem....could be reeds but again they go our rarely... I almost forgot...rebuild the fuel pump....given the Ethanol I rebuilt them every couple of years..cheap kit and one less thing to worry about...let us know what you come up with...very interesting and frustrating for sure........

 

[V-Tech]

Re: 60 HP Mercury 2 stroke outboard has lean misfire

The problem seems to be somewhat intermittent so I wonder if the timing or the dirt in the jets could be it. Would any of the suggested checks cause an intermittent problem...like a fuel pump? I don't see why the jets would all of the sudden be incorrect when it ran fine for 11 years.????

 

[V-Tech]

Re: 60 HP Mercury 2 stroke outboard has lean misfire

As it turned out there was a small leak in the primer bulb. apparently enough to draw air and lean out the air/fuel ratio. replaced bulb and the problem was solved. thanks for the input.

 

[1nebel0]

Re: 60 HP Mercury 2 stroke outboard has lean misfire

Great...that was a cheap fix..