wrote in message
...
This isn't a response to anyone, I just volunteer it for searchers
like me. I recently bought an old 40 horse Johnson outboard.

On a marine solenoid, battery is wired to one of the small posts, and
ground comes in via the starter switch, etc. to the other small post.
That's it, the two small posts are both ends of the winding.

In an automotive solenoid battery comes in to one small post via the
starter switch. That is one end of the winding but the other end is
connected to the solenoid case, and is thus grounded permanently to
the auto chassis. The other small post, if there is one, will become
energized along with the starter cable during the time the solenoid is
operated. I was told that this supplies a full 12 volt jolt for spark
during cranking. It bypasses the ignition resistor. (I suppose that is
where I got my smoke and sparks from. Luckily, when I jumped back I
jerked my jury- rigged wires loose.)



An ignition-protected marine-rated solenoid also has a sealed casing so that
sparks during contacting cannot ignite any gasoline vapors that reside
inside an outboard motor cover. Fiberglass motor covers disintegrate and
burn quickly when gas fumes ignite inside them and explode.

The reason most marine solenoids are wired with one terminal for B+ and the
other for ground circuit is for the safety start-in-gear protection. Usually
the there is a shift switch on the gear linkage that completes the circuit
when in neutral or completes the circuit if the throttle is advanced too
far. On other motors it just is wired to ground as the control box contains
the neutral safety switch on the B+ side.

Some outboard solenoids are like automotive style with a grounded mounting
plate and the ignition bypass terminal provides voltage to latch the main
power relay ON so the electronic control modules power up.

Bill Grannis
service manager