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Magneto Breaker Points

H. I. McDunnough

H. I. McDunnough

Regular Contributor
After dewinterizing and warming up my 1978 Mariner 40B (started right up), I gave it a little gas. It started getting some smoke. I gave it a little more and it cleared out. It did this last year, so I moved up to the next hotter plug. It helped a little. I pulled the plugs. Sure enough, they were oily and the bases were black (only black on one half of the #2).
I tested the spark; 3/8" on #2, but only 1/8" on #1. I replaced the spring clip in the boot on #1 (it had been reused before). Still tested bad. I tested the secondary coils; they seemed OK (the primary is new). I then pulled the flywheel. I tested the breaker points. They showed some resistance; one more than the other. I cleaned them with solvent and a business card. They are almost there; with in .1 to .3 ohms. I think I've found the problem, but I don't want to pull the flywheel again. Would you say it's good now? Should I file them first? I've heard that filing can ruin them. Or should I just replace them?


I'm also convinced that I have the timing retarded too far. Maybe that's why the oil is not burning all the way off. I'll see once I've addressed this issue.
 
faztbullet said:
1000 grit or finer crocus cloth and alcohol...
Click to expand...

I'm glad you brought up crocus cloth. I've always wondered what was different about it; so I checked it out, after reading your post.
I've always thought, "Why not use emery cloth". And I've always heard, "Don't use sandpaper, because it will imbed particles into the contact and ruin them".
What I learned was that emery cloth uses a mineral as an abrasive (emery or "black sand"). It used to be used to fit metal parts before machine grinding became the norm, because it would not imbed in the metal (go figure).
Emery cloth uses iron oxide which gives a smoother finish, but tends to imbed in the metal.

All this doesn't make me confident enough to use emery cloth, but it does make me leery of crocus cloth. Maybe that's why so many people say to stay away from sand paper.
 
We used a burnishing tool...looks like a throw away nail file...to clean relay contacts on pinball machines in the 1970s. It has the texture of the striker pad on a book of matches but only removed the carbon from the points. Don't know if they still make them or not.
 
I bought an ignition point file from an auto parts store. It is very fine. I'm just hesitant to use it. The contacts now look grey. I took a lot of oil and dirt off. Like I said, the resistance is down. To file or not to file; that is the question. Well, I guess I've wasted enough of your time. I'll make a decision, put the flywheel back on and see how the spark test comes out. How did you guys ever learn to work on outboards with out the internet.
 
Ignition point files leave no dirt.--------Points must me clean ( do not need to be polished ) so that they have no resistance to current flow.------------We used to be good students with excellent teachers and that is how we learned in the old days.
 
H. I. McDunnough said:
I'm also convinced that I have the timing retarded too far. Maybe that's why the oil is not burning all the way off. I'll see once I've addressed this issue.
Click to expand...
I just wanted to report back for anyone who might benefit from this thread.
I got the points cleaned up, and reset the timing. I also advanced the full retard setting a little, hoping it wouldn't load-up so much at idle. I then did a hot soak with Sea Foam. I then ran the motor; on smoke. I thought that did it. I shut the motor down. I noticed that it was to hot to put my hand on. I started it back up, tapped on the thermostat housing, and it cooled right down. Then it got too cold and started to smoke again. I assumed that the thermostat was sticking and replaced it. It doesn't smoke or load-up and have had no problems since.
 
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