1992 Johnson 120hp Looper

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ruffoceans

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May 26, 2009
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I have been having problems with low speed trolling the motor shakes and seems like it wants to stall. It runs fine once you give it a little throttle. It use to run like crap just at idle before i had the carb kits put in but know its just at low speed it does this. Plugs?? Wires??? Coils??? Thanx for your help...
 
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ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: 1992 Johnson 120hp Looper

You might want to de-carbon the engine, then rebuild/service your recirculation check valves.

I find trolling with QL77JC4 set at .040 gives better performance. Use XD-50 oil or add carbon treatment to the gas.

Put an inductive timing light on the plugs while running under idle load to check for double firing.
 
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ruffoceans

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Re: 1992 Johnson 120hp Looper

Thanx i actually ran a de-carb tank through it yesterday how long before i see a difference??? I am running different plugs i will try those plugs this am thanx for your help......
 
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CharlieB

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Apr 10, 2007
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5,617
Re: 1992 Johnson 120hp Looper

LOOK down the carb throats for ANY fuel, (engine off) while pumping the primer bulb.

Even one float set too high can slightly flood that cyl and cause a rough idle, yet run fine with the throttle opened.
 
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ezeke

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Sep 19, 2003
Messages
12,532
Re: 1992 Johnson 120hp Looper

After de-carb, I usually find my check valves clogged.

The de-carbon treatment should show some quick results in terms of heavy smoke as the carbon burns off while running, but a dirty motor can take up to three treatments. You get best results using the kit that connects to the schrader valve on the primer solenoid.
 
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ruffoceans

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May 26, 2009
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Re: 1992 Johnson 120hp Looper

Still having the same problem im gonna try another tank of de-carb i also noticed it ran a bit better with the motor trimmed higher i also changed the plugs i will let you know how i made out.. Stripers are running awsome here i need to get out......
 
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mattandmelissa

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Joined
Dec 18, 2007
Messages
24
Re: 1992 Johnson 120hp Looper

Make sure you run the right spark plugs. I had a similar problem with mine and changeing to the champions that are recommended fixed it. Make sure you use the champion q series plug that was recommended others will mess with the electronic ignition.
 
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