johnson acting funny

[baconbiscut]

i have a 1955 johnson 5.5 hp motor and every so often the motor will run fast or slow today it ran slow not planing my jon boat with just me in it and yesterday the motor ran fast and planed the john boat . in nuetral and revs up fine. i have been trying trying to solve the problem but i just can,t figure it out please help thanks

 

[Paul Moir]

Re: johnson acting funny

Don't rev the outboard in neutral. It harms the engine and is useless as a diagnostic since it doesn't tell you anything.

Check spark. That's often the trouble with those symptoms. Both cylinder's ignition system should produce sparks that'll jump a 3/8" gap. Set up a gap test w/ a couple nails in a board or a cheap adjustable spark gap tester.

If that turns up a fault, often the trouble is cracked insulation on the ignition coils. Fortunately it's easy to see that once you have the flywheel pulled.

What happens is, occasionally the ignition coil arcs over, and one cylinder misses. The funny thing about it is often they'll both fire at idle just fine, but not as you pick up RPMs. Of course, you shouldn't overlook cracked spark plug wires, dirty points, etc.

Click here

 

[F_R]

Re: johnson acting funny

Echoing what Paul said. Unless those coils have already been changed they are almost guaranteed to be bad/cracked. They always are on those old motors. New coils are available and will fix it right up. But don't ignore the rest of the stuff in there.