Re: Evinrude Speeditwin 6039 Starting Help

[Tom]

Gearhead,

(Is this Matt?) We can test all the condensers and coils you have. Call me at 509 three three nine, 3546 after 7:00.

A little background here… The condenser needs to store energy, then release it when the points open. Think of it like a gas can with an inlet and an outlet. The can has a certain size. The inlets and outlets can restrict flow if they are too small. And the can may leak. OK, hold that thought…

There are a few parameters that are important for use in a magneto. One is how much energy to store. That’s the capacitance (like the size of our gas can). Anything from 0.1 to 0.3 uF will probably get the motor going.

Another parameter is how quickly it can store or release the energy (the size of the inlet and outlet fittings on our gas tank). I think that’s the dv/dt value. Typical electronic capacitors have dv/dt values that are too low for our purposes, but special ones can be found with the right numbers. There is one you can get from DigiKey that works fine, the number is somewhere on this board.

The last value that affects use in magnetos is how quickly the energy will dissipate if the condenser isn’t hooked up to anything, the leakage rate (yep, our gas can may leak). Many meters measure leakage rate. The best ones measure it at a pretty high voltage. The homemade one with the neon light, or the one in the Merc-O-Tronic and Stevens testers, test at or near 120 volts. My Stevens tester has been a very good predictor of whether a condenser will work in a magneto. The Heathkit condenser testers, like the old C-2 and C-3 models, can test at higher voltages. I’ve found that a condenser known to be iffy will fail at 250 volts, but might appear OK at 150. So I like to test them at the higher voltage.

The stand up WICO condensers, with the screw terminal on top that were used in Scotts and Martins, are notorious for being bad. I’ve tested new ones and they failed. Every used one I’ve tested showed some leakage. Best thing to do with them is cut out the bottom, remove the guts, and put in one of the recommended capacitors from DigiKey. It’s a little bit of work, but retains the binding post on top that will keep wires and the strap from the points from getting caught by the flywheel.

I recently tested an original condenser from a ’30’s Caille, and it was fine. Well, there you go.

Testing coils is pretty straightforward. First you measure the resistance across the secondary. If it’s an open circuit, the coil may actually work by sparking across an internal gap. But that coil is doomed, as it will eventually burn away material and stop working. Then you measure the current required to throw a spark. If it’s too high, there’s something wrong with the coil. It may work, but probably not for long. There are charts available that tell us the recommended current each coil needs to work.

Hope this helps.

Tom