1970 Johnson 85, seems to misfire after engine warms up

makak

Recruit
Joined
Oct 5, 2007
Messages
5
Hi All,

I have a 1970 Johnson 85hp motor. The engine starts up no problem, after about 30min of boating the engine seems to misfire when I put it on full throttle( pop pop noises) I reduced the throttle a bit and it runs fine.

When I stop the engine, it didn't want to start again. towed it home, started the next morning and it started(turns on and off no problem).

I get the feeling it has something to do when the engine warms up, like a cracked coil somewhere which expands with heat which probably grounds the current or something. when the engine cools down, it starts/stops fine and runs ok until it warms up again.

Engine is not overheating, i have installed a tail tail water is coming out normally the whole time.


Any ideas?


thanks!
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 1970 Johnson 85, seems to misfire after engine warms up

Check your coil for cracks, if cracked replace it.
You might try running on muffs and spray your coil with a mister bottle and see it acts up, not a water hose but a mister bottle.
The dist cap and rotor are made out of a sort of plastic, could cause problems when warm.
Could be you have an amplifier about to fail also.
 

makak

Recruit
Joined
Oct 5, 2007
Messages
5
Re: 1970 Johnson 85, seems to misfire after engine warms up

Thanks for the great info Davie.

I will try that spray on the coil while running.
I hope its not the amplifier, i think they are hard to find for my model :(
 
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