40hp johnson,loss of power

[lowejohnson]

I have a 1983 johnson 40hp,has no power under load.idles,runs smooth.just no rpms under load.in neutral will wind up no problem.the bottom spark plug is not burning as clear or hot as top plug.could it be a coil or powerpack issue? is there a way to tes either.thanks

 

[Beek14]

Re: 40hp johnson,loss of power

You can get a spark plug tester for the plug boots to tell you if the electrical is good. Could it be the bottom reed valves? Not opening as well as supposed to or possibly broken?

 

[boobie]

Re: 40hp johnson,loss of power

When running under load, pull one plug wire at a time and see if you have a weak cyl. They should both drop the same rpm if all is well. If not you can narrow it down to a bad cyl.

 

[lowejohnson]

Re: 40hp johnson,loss of power

When running under load, pull one plug wire at a time and see if you have a weak cyl. They should both drop the same rpm if all is well. If not you can narrow it down to a bad cyl.

I checked the compression both cylinders 95 pounds,my neighbor has a 25hp johnson,has spare coils,can I use one of these,they look the like the same coil??