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

[jw-in-dixie]

Installed motorcycle coils on a Mark 20 using the existing points, gap and cond. Runs fine on a mower battery or =. We don’t need no stinkin’ Bendix coil$! 😉

[RICHARD A. WHITE]

Yuppers, hard to answer that question without more info…

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[1946zephyr]

I don’t know……looks like another case of "Billy Bob" mechanics to me. I figure puting factory parts on it and doing things right, is the best alternative. Why bastardize a classic motor? If coils are expensive……. so what? It’s part of the restoration game. It’s nothing compared to the total cost of restoring a good motor, anyways.

[amuller]

Your question is not framed very clearly. If your motor has fire-on-open points you can probably hook up a battery ignition. BUT, bear in mind that kickback may be more likely because, unlike magneto ignition, the power source is external and the motor doesn’t need to be turning at any speed to produce a hot spark. If the timing is significantly before top dead center, it may kick back. Can be a safety issue, especially if you are cranking it with a knob on the flywheel, or if you are using a rope and wrap it around your hand….

[mercuryman]

To Tom Manley you have a very interesting solution for a bad coil I am going to try it. I guess using a "orange drop Capacitor" is a no no also.

[jw-in-dixie]

In defense of Billy Bob, may I point out:

The Mark 20 powerhead was from a junk pile – there were no other parts to restore a full motor
I needed to see if it would run, without spending $100 on Bendix coils
The M/C coils cost $2 at a yard sale
I’m curious and want to try things, always trying to learn
The modification was very simple to install and remove, with no damage to the block
Indeed it ran and at 10% higher rpms than similar motors in the rat motor application that I run
Nothing ventured, nothing learned

I think perhaps Henry Ford was a Billy Bob – look what his tinkering led to

Cheers, JW 😀

[Tom]

quote mercuryman:

To Tom Manley you have a very interesting solution for a bad coil I am going to try it. I guess using a “orange drop Capacitor” is a no no also.

There is nothing wrong with the orange drop capacitors, as long as you use the correct ones. "Orange drop" covers a lot of products. Critical factors are capacitance, voltage rating, and dv/dt.

T

[wiscoboater]

Dont you hate that when the original poster asks a question and then just drops out…..

[melugin]

In the early nineties I was running a Speedifour on battery using two Honda 750 coils. Jon Wiggins had an article in the ‘Outboarder’ about the conversion he had. Had a switch to isolate the battery. Each coil would fire two cylinders at the same time. Motor would start at idle while seated at the controls. Demonstrated the rig pulling Dr. Wiggins on water skis at the Nationals in ’91 at Wenona. The temps dropped to the fifties that day.

[Author]

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