1965 Johnson 75HP Spark at coil, not at plugs

[oldjunker]

Hello everyone, I did my best to research this before posting to save any additional work from all the friendly folks on this forum. I have been scouring all the posts I could only find one regarding my situation that was close but it was not very descriptive. I'm not trying to be overly verbose here but I assume you need all available information. I am the proud owner of an old 1965 Johnson 75HP outboard (1st boat I've ever owned...). I bought the boat Thursday at 5 and was pulling tube at 7. The motor had set for a year unused, so before leaving i ran a hose into the lower unit make sure it was operating properly and to find out if this thing was going to run... I added fresh fuel mixed at 24:1 and threw in a battery and honestly to my surprise it fired up and ran pretty well. It was shooting a moderate stream from the hole on the upper portion of the lower unit, so I thought I would take it to a little local lake and see how it ran. It ran great, got up on plane and wound up like it should all night (2 hours o operation). Of course then the other shoe fell. As I was lining the boat up to get it back on the trailer, it acted like I had shut the key off. Instant stop and upon more investigation after it was on the trailer I found no spark on any plug. I disconnected the coil wire and found I have bright blue spark leaving the coil. Since I have spark leaving coil, I assume that the points, coil, and condensor were working properly, but I checked just to make sure. I could see the points breaking on both sets as they should and visually the pads looked fine. The cap looks good and the rotor does as well. I know that visual inspection doesn't always ensure proper operation, but I'm new to this whole marine world and want to cover all bases. If I lay the cap close to a ground while turning over I can see spark jumping from rotor button to ground, so I assume the rotor has to be bad.... My only reservation is on any of the old vehicles I've ever worked on, I have never seen a rotor that wouldn't carry fire..... If I'm all wrong here please tell me so... I have a rotor on the way but the anticipation is driving me NUTS!!!! I would like to get a good idea if this may fix me.... I've got a young son that can't wait to get back out on the water in the old heap Ok neither can I......
Thanks very much in advance,

Brian

 

[emckelvy]

Re: 1965 Johnson 75HP Spark at coil, not at plugs

It's very common on the old Belt-Driven mags & distributors to see rotors that become electrically compromised and allow spark to jump thru to the rotor shaft. Old inline-6 Mercs with the dual-point ign and 2-layer-rotors have the same problem.

I'm thinkin' you'll find lotsa good spark at the plugs once you replace that misbehaving rotor.

HTH...............ed

 

[F_R]

Re: 1965 Johnson 75HP Spark at coil, not at plugs

Yep. Have seen it many times. A new rotor comes with a little gob of insulating grease inside. Don't remove it.

 

[Evinrude Boater]

Re: 1965 Johnson 75HP Spark at coil, not at plugs

You can run it on 50:1 and let your son breathe a little better on the tube.

 

[oldjunker]

Re: 1965 Johnson 75HP Spark at coil, not at plugs

Success!!!!!!! I was so antsy I couldn't wait for the new parts to arrive..... I found a semi-local salvage outfit and picked up a cap and rotor for ten bucks. I threw them on and it lit right up! I will take the recommendation on remixing my fuel, I thought that since the motor had set a while a little extra lube wouldn't hurt. Is this a relatively common occurrence, to the point I should haul an extra rotor around with me?

Thank you very much for the wisdom.... my son will thank you too about four o'clock when I'm off work and we get the old pile back in the water!!!

Brian

 

[oldjunker]

Re: 1965 Johnson 75HP Spark at coil, not at plugs

I really appreciate you guys taking the time to post. It was very helpful to a newbie!

 

[Evinrude Boater]

Re: 1965 Johnson 75HP Spark at coil, not at plugs

I've never had a problem with the rotor. Wires, yes, points, yes.
The extra oil doesn't hurt, it just stinks riding behind the boat on a tube. I would mix extra oil on the last tank before laying it up for the winter just to give it a little extra protection while it sat in a Canadian winter.