Left my key on, battery drained down to 4 volts.

[tmfd]

2006 Mercury 40 hp EFI 4 stroke. Has the alarm horn by the key. I seem to remember something from my younger days about leaving an ignition key on and it will harm or "burn up" something or other. Is there any harm I may have done by leaving the key on and the battery draining to almost nothing? What was using the battery? I guess there is no Low voltage alarm either?

 

[MTboatguy]

You have to remember systems are energized when the key is on, I would put my battery charger on the lowest, 1-2 amps and hook it up and see if it will slowly start bringing the batter up to charge, if it has not set to long with it drained that far there is a good chance it will come back to life, also make sure the cells are up to full, if it is not a sealed battery before charging. Depends on what you have installed in your boat, on what drained it.

 

[Frank Acampora]

In old cars and outboards where spark was generated by a coil and points, the coil was energized by the battery. If you left the ignition key on when the points were at a low spot on the cam--in other words closed, current would constantly flow and you could possible ruin the coil, melt some wiring, or pit the points. Your 40 EFI does not have points and usually, these ignition systems are separate from the battery. I don't think that you will have harmed any running systems. But, I can be wrong. Why don't you check over at the Mercury Forum.

 

[gm280]

You may have dodged a bullet with the actual engine (maybe ?), but other things in the boat were probably running as well. So there is really no telling what could have been damaged without being there and testing things. Charge the battery back up. Maybe even take it to have it load tested and then try it out and see what works and what doesn't... :noidea:

 

[tmfd]

Thanks for the advice folks. I didn't mention that it is a deep cycle battery. I charged it back up, took about 8 hours. I'll see if she will hold the charge. I'm glad to hear that I probably didn't ruin anything other than maybe the battery. I am fairly certain that nothing else, pumps, lights, etc. was turned on. Just the key.

 

[Starcraft5834]

tm.. I left key on in mine last year I think... was too a deep cycle marine battery,, it was shot,, had to replace it,, that was it