Re: Using a car coil outside the 2 stroke block

[Tom]

I was trying to ease into this topic, but that may not have been the best approach…

The diagram shown for running a battery ignition system using the original points has no provision for disconnecting the coil when the motor is not running. That would have to be engineered into the installation. If the points are closed when the motor is stopped, as in the case for most of the magneto systems we deal with, the coil and possibly the battery will cook. I guess you could turn on the system at the same time you pull the rope.

Now if the system is of the type where the points close only at the point of firing, the system shown will be OK. (Not great, though, if the motor stops with the points closed. This situation is unlikely, but possible.) Some early motors had this type of system, so they can be adapted easily. The Evinrude RBM is this type, so hooking up an external coil is pretty simple.

Here’s an alternative that I’ve used successfully on a Mercury Mk 5 with the Bendix Scintilla coils. Replacement coils would have cost me four times what I paid for the motor, and I’m not really into the green motors…

If the original coil is still in place, and just has a bad secondary, there is an alternative to the battery system. If you have a coil with a bad secondary and you try to start it, you’re still generating current in the coil primary circuit. You can use that current to fire another coil mounted externally. Detach the wire that normally goes from the coil to the points, and add on some wire to extend it out from under the mag plate. Attach it to the primary lead on an OMC Universal coil, and mount the coil on the block of the motor with the OMC coil ground wire grounded to the block. Then run a spark plug wire from the OMC coil to the spark plug. This may work better if you remove the bad secondary from the bad coil, I can’t remember whether I did that.

In the case that Tubs shows, a battery fired coil is used mounted to a RBM. That’ll work since the points close to fire on that motor. The Model T buzz coil will work a LOT better on the RBM, though. The motor will idle slower and never skip, since multiple sparks occur with the buzz coil. you only get one with the later battery fired automotive coil.

Tom