1969 Johnson 18HP Manual for Carb Adjustment and Cleaning
Motor is running rough will not Idle down will not produce top speed with WOT. Looking for info on how to trouble shoot and repair problem, Motor starts Runs rough Will not Idle down to let you shift and high speed is not even close to what it should be. Any help? Sorry this is a 1959 Johnson 18hp
Re: 1969 Johnson 18HP Manual for Carb Adjustment and Cleaning
If it were my motor, I'd:
1. Check compression. If compression is good, all else can be addressed with a little effort and less than $150 in parts.
2. Check spark with a spark tester - should jump at lease 1/4" gap and be a nice blue-white snappy spark.
3. If it has good spark, get a carb kit and clean/rebuild the carb. Lots of info here on that subject. Replace gas lines.
4. If no spark on either or both plug wires, you'll need to pull the flywheel to see what's going on underneath. Could be bad coils, dirty/worn or misadjusted points, bad condensers, wires or spark plugs. You may be able to check coils and adjust points if your motor has an inspection port on top of the flywheel.