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Johnson 150 cough/stall at trolling speeds

L

loopyboat

Member
1992 Johnson 150hp TJ150GLENC

After rebuilding all 6 carbs and replacing the float bowls and seals I'm still having a problem with my motor having an intermittent cough/sneeze and sometimes it stalls when going very low at trolling speeds. It seems to happen more when it's warmed up and been running for a while. WOT the engine runs great.

There is good spark on all cylinders and compression is good. Fuel is new, and lines are in good shape. I'm really puzzled what could be causing the problem. Should I try new spark plugs? Perhaps going up a jet size in one of the low speed jets?
 
I don't know the history of the motor but it's been having this issue since I bought it. I'm in Upstate NY on lake ontario, I don't think I'm at a high altitude. The stock jet sizes for this motor correspond with the jets that are in it now, so I'm not so sure that's the problem now that I think about it.

As for the idle speed, I think it is idling maybe a bit too low, I adjust the idle by the clickers on top of the flywheel cover correct?
 
sound like a lean cough or sneeze to me. try adjusting idle mixture screws. boat needs to be in water, warmed to operating temp, and in forward gear with its movement unrestrained. take your time adjusting one at a time and readjusting. they are very sensitive.
 
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