1977 85 hp johnson only running on 3 cylinders

[boatman172002]

Only runs on 3 cylinders at high speed. All coils OK. All spark plugs OK. New power pack. Engine idles fine has spark on all 4 cylinders. When run up to full throttle only runs on 3 cylinders. When I pull all 4 plugs it is always the bottom left cylinder, when facing the back of the engine, that is always the plug full of gas not firing at full speed. Have switched coils, plugs and new power pack but always bottom left cylinder with wet plug. Any suggestions. thanks, boatman172002

 

[clanton]

Re: 1977 85 hp johnson only running on 3 cylinders

Check timer output to pack, and pack output to coil,with engine running at RPMS where you lose spark.

 

[JB]

Re: 1977 85 hp johnson only running on 3 cylinders

Howdy, Boatman.<br /><br />If the checks that Clanton suggests bear no fruit, check your compression, try spraying some fuel mix into the carb throat that feeds that cylinder when it is misbehaving and take a look at your reeds.<br /><br />I suspect that Clanton is onto your problem.<br /><br />Good luck.

 

[DJ]

Re: 1977 85 hp johnson only running on 3 cylinders

Boatman,<br /><br />Do you have the spark plug wires crossed?

 

[boatman172002]

Re: 1977 85 hp johnson only running on 3 cylinders

no, spark plug wires are not crossed

 

[boatman172002]

Re: 1977 85 hp johnson only running on 3 cylinders

no, spark plug wires are not crossed

 

[BKool68]

Re: 1977 85 hp johnson only running on 3 cylinders

Is the boot on the plug wire sliced and grounding out to the engine latch?

 

[novacane]

Re: 1977 85 hp johnson only running on 3 cylinders

try shortin up the gap on that 1 plug to like .020<br />it will that less kv to fire it see what happens

 

[boatman172002]

Re: 1977 85 hp johnson only running on 3 cylinders

Thanks, I will check that out and try the different gap on spark plug