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35hp JohnsonNeed help

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Henry F

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I have a 35hp johnson 1981 mo

I have a 35hp johnson 1981 model. It starts easily has 128 and 130 psi compression. It seems to run pretty smooth but doesnt seem to develop all its power. While running if I pull the top plug lead out it will still run ok..little rough.
If I pull bottom lead off it seems like it loses most of its power...will only run on a high throttle setting. When I remove the spark plugs top one looks clean but no signs of water...just seems like alot of oil/fuel. Bottom plug looks normal maybe slightly wet. Have replaced fuel pump and no fuel leaks out of the carb.
 
"Henry.... The compression sou

"Henry.... The compression sounds okay but you don't mention the spark. With the s/plugs removed, the spark should jump a 7/16" gap with a strong blue lightning like spark (a really strong wide snap!). Rig up a spark tester where you can set that gap, or use a proper size philips screwdriver that will fit inside the wire terminal that's within the rubber s/plug boot. You can then hold the shank of the screwdriver the approximate 7/16" away from the powerhead (block).

If the spark is faulty, let us know. Note that the spark plugs should be Champion QL77JC4 or L77JC4 plugs, gapped at .040 . The "Q" indicates a resistor type plug which helps to quiet interference (noise) with any electronic equipment.

However, if the above checks out okay, the problem is most likely with the carburetor. You can try the adjustment as listed below but if no improvement results, I'd suggest you remove, clean and rebuild the carburetor, then adjust it. Be sure to manually clean the brass fixed high speed jet that's located in the center bottom portion of the float chamber.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

Joe
"
 
Thanks for the info joe.
As

Thanks for the info joe.
As far as spark goes I haven t checked it properly yet but when I start the motor on the weaker cylinder it will run evenly at 3/4 throttle and beyond. Any less and it wont run. this made me assume that spark is ok. Could it still be a spark issue? Spark plugs are new L77JC4 and i can swap them with no difference. I will remove and rebuild the carb but somehow I dont think its at fault because plenty of fuel is getting into the motor. Could it possible be an air leakto the lower cylinder resulting in me setting the carb too rich and drowning out the top cylinder?
Thanks again.
Henry
 
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