ignition switch question

[tom61]

The ignition switch on my boat is two parts: the keyed ignition and a button for the starter. I inadvertently left the key on a couple of days ago after the engine was stopped and discovered that the battery drained overnight. Which I admit surprised me a little. There were no electric loads turned on anywhere that I can see, except for the bilge pump which runs off the same battery, but it's independent and didn't have a lot to do, either.

Without the engine running, I can't think of a route to complete the circuit, except maybe for the ammeter. So my theory is that the battery discharged through the ammeter and the coils of the generator (old engine, not an alternator).

My questions: Am I ignoring another obvious route to ground on a stopped engine? And: Is this a sign of a wiring problem I should look into? Or is this just the normal punishment for this kind of carelessness? Opinions welcome, thanks.

[Dave Neptune]

Leaving the key on is leaving the power on to the ignition and it will drain the battery completely. The other downside is that you probably now also have a fried the (dead) coil. When you get some juice back in the battery check for spark if it does not start easily and turn off the water valve so you don't get water into the engine through the exhaust.

Dave Neptune

[JOHN COOKSON]

Originally Posted by tom61

I inadvertently left the key on a couple of days ago after the engine was stopped and discovered that the battery drained overnight.

The only time the key was in the slot on my boat (when I had one) was when the engine was being cranked or running.
If you would have been lucky the points (or EI) would have been open but it doesn't sound like it because the battery is flat.

ex TRUE GRIT

[tom61]

So the route to ground is the primary coil, plus the distributor having stopped while the points were closed? That makes sense.

And the coil seems to have survived its ordeal. The engine started no problem with the second battery. But I'll acknowledge dodging a bullet there. Thank you.

[Sam]

You got some great advice. I would still watch the coil for premature failure from the ignition being left on. A little running time and some excessive heat build up and it could still fail you and shut down the engine when you need it most. The resistance could test ok statically but once it is running for a while it could change. If it was me, I'd at least carry a spare if not change it out.

[edwardc]

+1 on carrying a spare.