Outboard Motor Coils

[David M Parrish]

> From:          "Jim Staff"  <staffj at freenet.msp.mn.us>

> > This engine also uses unusual spark plugs.  There are no conventional
> > electrodes.  Looking end-on to the plug, it looks like an archery target --
> > three annular rings.  The center ring is the center electrode, the second
> > ring is the insulator, and the third ring is the outer electrode (case).
> > Viewed from the side, the plug is flat across, with the insulating ring
> > slightly recessed.  The spark occurs at any point across the faces of the
> > center and outer rings.  These plugs last a long time, and, of course, there
> > is no gap to adjust.

> The questions...
>   1. How far do these suckers stick below the head?
>   2. How much volatge is used to drive the puppies?
>   3. How large are they?

I believe surface gap plugs can only be used with CD systems and have 
no extension past the threads and probably none into the cylinder. 
Most likely, they're specifically for two-stroke engines. That's the 
most I can dredge up from memory, since it's been a long time since I 
read anything about them.

As to using outboard marine coils, aren't they driven from the 
magneto and/or alternator just under the flywheel? Hard to say just 
what voltage they're being fed.

---
David Parrish
Man, it's been a while
since I fooled with outboards!