Cylinder cuts in and out on 90HP Johnson

J

jsmalley812

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I have a 1982 Johnson 90 HP that just recently developed a problem. On idle it runs a little rough but not too bad. On full or 3/4 throttle it feels like one cylinder cuts in and out. I changed the plugs and it's no different. How do I know if this is a coil or power pack problem?
 
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Walker

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Re: Cylinder cuts in and out on 90HP Johnson

Clean the coil grounds real good and try her again.
The only way to really diagnose the problem is to do a spark test while its acting up.
If you are not loosing spark then you prtobably have fouled carb/carbs
 
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AlanR

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Re: Cylinder cuts in and out on 90HP Johnson

get a manual and it will tell you how to test the Powerpack.
 
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jsmalley812

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Re: Cylinder cuts in and out on 90HP Johnson

Walker said:
Clean the coil grounds real good and try her again.
The only way to really diagnose the problem is to do a spark test while its acting up.
If you are not loosing spark then you prtobably have fouled carb/carbs
Click to expand...

I never thought of it being a carb problem but I guess thats possible as well. It's really strange I can be zipping along fine and then suddenly the boat slows down about 5mph then the cylinder catches again the boat takes off. First time this happened I pulled the plugs and one was wet. I changed the plugs, went for a ride and I had the same problem but when i checked the plugs none of them were wet.
Is there a way to clean the carbs without taking them off the engine ?
 
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AlanR

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Re: Cylinder cuts in and out on 90HP Johnson

nope u gotta take the carbs off the motor to clean em.
 
jtexas

jtexas

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Oct 13, 2003
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8,646
Re: Cylinder cuts in and out on 90HP Johnson

hit the choke/primer switch when it cuts out...if it picks back up, suspect the carbs.

Have a timing light? Might be able to track down a hi-speed misfire to a specific cyl, then narrow it down by swapping coils. You might want to have a helper aboard for this operation. 8)

not a substitute for a factory shop manual, but some good ignition troubleshooting tips here: http://rapair.com/Portals/0/downloads/TroubleshootingGuide.pdf
 
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