Sluggish Johnson

[Bartman]

1977 70 horse Johnson. Starts fine but does not have power. The way the boat acts in the water, I would of said it's the carbs. If you get into the throttle slowly it gets up to about 10 mph and then starts bogging down. I COMPLETELY disassembled all three cards and cleaned with carb cleaner and compressed air. When I started it on the ear muffs, I could tell it did not fix the problem. This motor has always idled like a new one. In fact, the thing looks brand new inside and out. I bet it don't have over 20 hours on it. It would idle down and die. It will rev up (on the muffs) but acts like the timing could be off (sluggish). I noticed while holding the R's at around 2500 that one of the cylinders would randomly miss. Here's what I plan on doing/checking, 1)new spark plugs 2)checking flywheel key 3)inspecting coils for cracks and loose wires 4)checking power pack with ohm meter. Any other suggestion or comments are more then welcomed.

Thanks for your time!
Bart

 

[samo_ott]

Re: Sluggish Johnson

That's a popular engine but out of my knowledge area. You might try reposting with a subject referring to the year and hp as then the right folks will see it. It seems like you're on the right track now, if the carbs are good it's in probably in the ignition.

 

[HighTrim]

Re: Sluggish Johnson

First off I hope you're not revving that motor over 1500 on the muffs, your motor will go into thermal runaway, causing catastrophoc consequences. Start at the top, checking spark and compression, post your findings and troubleshoot from there. The spark should jump 7/16 of an inch with a strong blue ZAP!! Do you have a manual for the timing check? Make sure your plugs are torqued to 18.5 to 20.5 ft/lbs and they are in good condition. They should be L77JC4 or QL77JC4.