1976 Evinrude Magneto Troubles

[catalyst-519]

Hey Guys.

This is an addition to my previous post about my 1976 Evinrude 9.9 and the misfiring troubles. I've spent a lot more time trying to get to the bottom of this and here's what I've found so far.


Went to the marina to buy a new coil and the mechanic suggested that before I buy a new ignition coil I swap the two of them and see if the misfire occurs on the bottom cyl, as it was occurring on the top cyl once the motor reached operating temp. In addition, the low idle is really rough and often misfires or coughs out.

I swapped the coils, got the motor up to temp and the top cyl is still misfiring. When I pull the top spark wire, the misfire stops, until the cyl loads up and stalls. This says to me it's not a problem with the top ignition coil.

After reading the article at

www.sschapterpsa.com/ramblings/Johnson 9.9_15.htm

This guy suggest that it's likely bad condensers and that swapping these may solve the problem.

I pulled the flywheel and see that there are 2 additional coils. 1 single and 1 double. I suspect that the single is the ignition and the double is the charge coil, but I really don't know.

If anyone could take a look at these pics and help me out it would be great.

My question: Should I be replacing both magneto coils, points and condensers all in one go, or can I get away with one coil and the condensers. IF so, which coil is the likely culprit.

I'm lost and this is the last attempt before I go to the mechanic but I'd rather not if I can handle this myself.

Help is greatly appreciated.

Cheers---519

 

[5150abf]

Re: 1976 Evinrude Magneto Troubles

Had a similar problem last year, was convinced it was an ignition problem, $150 later I cleaned the carbs correctly and that turned out to be the problem.
if you haven't cleaned your carbs recently try that, it is free and easy to do.
Just a thought.

 

[CATransplant]

Re: 1976 Evinrude Magneto Troubles

Only the single coil has anything to do with ignition. The double coil is part of the battery charging system for electric start models.

There should also be two coils mounted on the exterior of the engine, which have the plug wires on them. So, if you swapped those two and the problem stayed with the top cylinder, while the other ran fine, the problem isn't with the coils at all, either the one under the flywheel or the external ones.

Now, focus on the point sets and the condensers. Check to make sure that all connections are tight and that the gap is properly set on both sets of points. It's tough to test condensers in a real way. The best test is a replacment of them...if that fixes the problem then one was bad.

What I suggest is that the points for the #1 cylinder (don't know which one that is) are out of adjustment. If that's not the case, a loose connection or an abrasion of one of the wires leading to your external coils is causing an intermittent short or open circuit. Condensers are cheap, so you can replace them before popping the flywheel back on (torquing the nut properly.)

Follow the wires from the points to the external coils in detail. If there's a clamp, remove it and look for crushed wires. Somewhere in that relatively simple system is a flaw. Find it and you're done. It's neither set of coils, though. Your substitution test rules them out.

 

[CATransplant]

Re: 1976 Evinrude Magneto Troubles

Look at the leftmost photo in your post. Look at the wire going from the coil to the left point set. It seems to me to be badly positioned. Check that wire closely, especially where it crosses the points pivot and goes down in that cavity. I'm betting your problem is there. It looks to me to be rubbing on the points arm, and on a sharp edge.

 

[catalyst-519]

Re: 1976 Evinrude Magneto Troubles

Thanks CAT

Checked and repositioned the wires. Same deal. Is it a general rule that when changing the condensers you change the points as well.

I'm probably just going to bring it in and bite the bullet. I just want to be back on the water instead of friggin around with this thing peice by peice.


Thanks ---519

 

[CATransplant]

Re: 1976 Evinrude Magneto Troubles

Normally, I'd replace the points and condensers as a set, unless I looked at them and the points were new and the condensers weren't.

 

[F_R]

Re: 1976 Evinrude Magneto Troubles

Can we assume you have tried a new set of spark plugs? We had a LOT of plug troubles with those motors way back when they were still new. Sometimes we couldn't keep brand new engines running for the weekend. OMC couldn't even fix them to keep them running. I guess eventually they did, but they drove us nuts at first.