Johnson 40 horse melting coils

[steve0361]

I recently aquired a 1975 johnson 40 horse outboard on a trade and it was under this guys porch lying on the ground. I imediately ran new battery cables and shorted across solenoid to check compression. Good even compression on both cylinders but during this brief test one of the coils got really hot and started smoking. I disconnected the battery quickly but the coil was damaged badly. only took a few seconds. Now the coils were very rusty and both were cracked. I removed the burnt coil and tried this again only to hear sizzling and the second coil was getting hot so I disconnected the battery again. Does anyone know if old rusty coils would do this or is there likely a different problem. The points and coils under the flywheel look like new and I can not find any short circuits in the wiring anywhere. I have checked the wires and connectors at every location.

 

[bktheking]

Re: Johnson 40 horse melting coils

Probably needs a full ignition tune up, points/coils/condensors/wires/plugs. Coils sound like they were shorted internally. Cracked coils=immediate replacement. Try coils first, points /cond may be ok.

 

[F_R]

Re: Johnson 40 horse melting coils

That motor has what is called the "Low Tension Magneto". Suffice to say that it generates its own electricity for the ignition system and is not powered by the battery. Through some sort of a wiring error, you are applying battery power to the ignition system....a no-no. More than likely you are using the wrong type of ignition switch. Or are you "hot-wiring" it?

 

[restornator]

Re: Johnson 40 horse melting coils

wouldn't crossing the battery cables overload his coils. If he grounded the + to the crankcase, it could very easily fry them, you'd also notice the flywheel rotating counter-clockwise

 

[bktheking]

Re: Johnson 40 horse melting coils

That motor has what is called the "Low Tension Magneto". Suffice to say that it generates its own electricity for the ignition system and is not powered by the battery. Through some sort of a wiring error, you are applying battery power to the ignition system....a no-no. More than likely you are using the wrong type of ignition switch. Or are you "hot-wiring" it?

Battery for starter and that's all one would hope? Weirder things have happened.