1968 Johnson 40HP sluggish

[liljewel]

Had our boat on the water, idles great and runs at low speed great, but won't throttle up. Full throttle is a crawl. Have checked to make sure it's getting fuel, cleaned the carb etc.
Husband pulled the top spark plug and nothing changed, the engine continued to run. When he pulled the bottom plug, the engine quit. He tried rotating the plugs and it continued to do the same thing. Top is not firing and no spark.......can someone maybe shed some light on what the problem might be?

 

[F_R]

Re: 1968 Johnson 40HP sluggish

Had our boat on the water, idles great and runs at low speed great, but won't throttle up. Full throttle is a crawl. Have checked to make sure it's getting fuel, cleaned the carb etc.
Husband pulled the top spark plug and nothing changed, the engine continued to run. When he pulled the bottom plug, the engine quit. He tried rotating the plugs and it continued to do the same thing. Top is not firing and no spark.......can someone maybe shed some light on what the problem might be?

I noticed you said "husband", so I'll be nice. He finally figured out the problem. It obviously is running on only one cylinder. He did just what countless others have done, cleaned the carburetor in an effort to fix it. The carburetor may or may not have been dirty, I don't know. But a dirty carburetor won't make it run on only one cylinder when there is only one carburetor like yours is. The carburetor feeds both cylinders at the same time. There is no way it can only feed one.

Now he has to pull the flywheel and see what is the true problem. Could be coil, could be dirty or worn out breaker points, could be condenser or wires. He will need a suitable flywheel puller to get it off and a torque wrench to put it back on. Use that torque wrench and tighten the nut to 100-105 foot pounds. Ignore the torque and risk destroying the motor.

Oops, sorry, I have to back up. Before doing anything else, do a compression test. If there is no or low compression on that non-firing cylinder, you have a different problem.