20hp Johnson running rough

[rudycard72]

I got this 1970 20hp johnson seahorse last year and had it out several times, it ran pretty rough and sputtered a little but still ran. I rebuilt the carb this winter and I am now having trouble. I can get the motor to start but when in gear it won't accelerate much and makes a fairly loud sputtering type sound that kind of sounds like an air leak.Do you think I did not clean the carb out good enough,the gaskets aren't sealed, or maybe just a fuel/air adjustment? Any help is greatly appreciated.

 

[Loggerhead Mike]

sounds like its choking itself out. run it for awile and check the plugs color

make sure your float needle valve isnt sticking at all and closing (sealing up) properly

then i'd reset the high and low speed jet adjustments

if you think you may have a vacuum leak spray choke clean around the gaskets on the powerhead. listen for it to rev up slightly or choke down

 

[rudycard72]

I checked the plugs and they are pretty black, they were new plugs at the end of last season maybe ran 4 or 5 times. What does black plugs indicate?

 

[Oddagus]

Black deposits usually mean fouling, too rich. I would have the compression checked on the motor since it is fairly old. I just went through this with a 8 HP Mercury. I was a low hour motor but it had a stuck ring because ants had gotten in the engine. A compression check will tell you if the engine is sound enough to spend more time and money on it.

 

[Whoopbass]

Check the spark. If its weak then your not getting a total burn.