Will a rusty magneto work?

I have a 1964 Evinrude 75hp V4 that has a weak white spark and #4 is intermittent. I have cleaned and gapped points and spark plugs but still have a weak spark. I took the coil out of the distributor and noticed the magneto is all rusty. Will this affect the spark? How should it be cleaned and protected from moisture? How can the points, condenser and coil be tested?

Re: Will a rusty magneto work?

if the area between the magnets and the iron is rusty, it could efect spark. I clean these areas with fine sand papper. you can use an ohm meter to test the points open will be a verry high reading and closed should be almost "0" reading, on a low scale with the wiring disconected from them. the condenser (disconected of course) on a high scale should start at a low reading and gain to a higher reading, NOTE be sure and discharge it by shortung the lead to ground or its case. the coil if it does not have cracks in it should be fine. I dont think I would try to put anything on it to protect the internals from moisture (maybe WD40) but try to find where the moisture was/is getting in! Just a thought<br />Richard

Re: Will a rusty magneto work?

I used emery cloth to get the rust off. If the magnets are strong it should be fine. I agree with rwise, find the cause of the moisture.

Re: Will a rusty magneto work?

I think the moisture in the magneto is just from condensation the same as the moisture on my bench vise in my unheated garage.<br /><br />I will get the magneto and coil contacts cleaned up but I need help in tracing the weak spark back from the plug to the magneto. I don't want to just replace everything. Any tips on how to test the spark plug wires, condenser, ignition coil and even the effectiveness of the magneto? I don't have a lot of diagnostic tools but if there's something I can do with a multi meter to eliminate components, I would give it a try before replacing parts or taking the distributor to a shop.<br /><br />I've tried to remove the plug wires from the distributor cap. Are they screwed in or just pushed in?

Re: Will a rusty magneto work?

you can test the points, with the wire/s removed, closed should give a near 0 reading on a low ohms scale, open should give a verry high reading on a high scale, conenser should (discharge it first) give a reading that jumps to a low reading and then gains to a high reading. If you test the coil this way you can get shoked, the power output of the meter is enuf to put out a fare charge on the out put side, just enuf to bit! I don't know the ohm reading for you coil, but if it has no cracks in it then its most likely good. Give it a good cleaning, and relub the bearings I find them to be dry verry often.

Re: Will a rusty magneto work?

The condenser has one wire to the points and the mounting clip screws to the ignition plate. Should I attach one lead from the ohm meter to the condenser body and the other to the lead? How do you discharge a condenser?<br />I've tested the points, they seem fine.<br />I pulled the magneto and coil and cleaned all the rust off the magnets.<br />Tested the plug wires and found one that was bad. I was told the wires turn out of the distributer cap. So I did. I appears the crimped end stayed in the cap and the wire came out with 1/4" of bare wire sticking out. Is there a crimped end on these wires? Should I turn it or pull it out of the cap?

Re: Will a rusty magneto work?

I dont think there is an end on those wires, they just screw (turn) in. If you look inside where the wire/s go there should be a pointy thing that pokes up inside the core of the wire (at least there is on mine but its older) If the condesor is still mounted discharge it by shorting the single lead coming out of it to ground (the metal case if its pulled) it may not have a charge left in it just a safety for you and you meter.<br />Richard

Re: Will a rusty magneto work?

Thanks Richard,<br />I got a boat shop to pull the faulty wire and replace it. It had an end crimped to the wire and it had a threaded portion that screws into the distributor cap. Had to re-use it since it was Friday afternoon and no time to wait for new.<br />I cleaned up all the magneto magnets and the coil contacts, put it all together and it fired up and ran nice (for a forty year old).<br />Now my problem is the boat. I took the kids tubing and when I stopped for dinner the boat filled up with water up to the back seats. It was truly mixed emotions Friday night. Too bad it wasn't just the plug. I'm taking a crash course in beam and floor replacement now. I'll be changing forums now. Thanks for your help. Maybe I'll hear from you in boat restoration/repair.