Ignition Switch Left in "On" Position

[rognvald]

We've been at anchor for 2 1/2 days. I noticed a larger than normal usage in amp hours and checked my batteries with a multimeter. I discovered my wife had left the ignition switch in the "on" position when she shut the engine down. Besides the obvious battery draw, could any other damage have been done? I have a Yanmar 3GM30F. Thanks, Rognvald

[Danm1]

Don't know the answer, but shouldn't the alarm have been sounding? Mine blasts whenever the key is on and engine off.

[wingless]

Thank goodness for having the better half to blame for stuff...

On my boat the engine hour total counter will NOT increment with the switch in the ON position unless the engine is also running.

Your counter may or may not have incremented.

[a64pilot]

I believe the power draw comes from the alternator being powered up through the alternator regulator.
I don’t think it would hurt it, but I guess maybe over time it could have gotten hot as there is no cooling?

As said earlier, I guess you don’t have a low oil pressure alarm?

[rognvald]

Hi, Pilot. Thanks for your input. I discovered two issues that previously were fine: LP alarm and hour meter buzzing and not working. If the lp alarm was working, this would not have occurred. So, no other problems than obvious battery draw possible? Thanks, R

[a64pilot]

I don’t know your boat obviously, but normally the Hobbs meter is powered, but won’t run as it usually is set up so that it takes oil pressure to complete the ground and make it work.
And of course I believe usually the alternator regulator receives power so that it can regulate alternator output.
That is all that I am aware of on the average boat, but of course yours may have other things like engine blowers or I’m not sure what else.

I doubt that it hurt anything, crank it up and see.
I do think you may want to get the low oil pressure alarm fixed though.

[rognvald]

Thanks 64 for your great feedback! When we return from our cruise, it will be on our short list. Thanks again, Rognvald

[Locquatious]

In the On position, the alternator field coil is powered and draws ~3.8A from a 12.6V battery. The regulator will be fully powering the field coil because the battery is below the voltage control point.
You may want to inspect the field wire to see if the insulation got hot or the wiring looks oxidized especially at connections. Also check the resistance of the field coil to see if it is in spec.
For the standard 55A alternator the coil resistance is 3.34 ohms @ 20°C. Not sure which blade, but disconnect the plug on the alternator and look for a resistance matching that value.

[captlloyd]

Seeing how you have a diesel, most likely no problem at all. Older gas engines had points which could burn the contacts if left on for any length of time. It would just result in the engine not starting.

[jpstevens]

On my boat I think that the auxiliary fuel pump would be running. I also agree that the alarm should have sounded. Mine does.