WHIPLASH

Turning off my battery switch does not turn off the bilge pump, blower or stereo either. They are directly wired to battery 1 and , apparently, none of the problem as they have not drained any battery. You may have to check what is directly sent to the battery(ies) and what goes through the switch.

RLW

A blown diode in my alternator would drain my battery. It still charged but when the boat was not in use, it would slowly drain the battery. I replaced alternator and problem was solved.
Alternator is a four wire, 55 Amp Mando .

Outdrive1

I have a charging system on my boat. When ever it's parked I plug it in for a few days and and plug it for a few days. It's an automatic charger but I still like to cycle it on and off myself. I usually plug it in a couple of days before I go out. No big deal, at least I have the piece of mind that when I go to use my boat my batteries will be fully charged. I have four yellow top optimas BTW and I know that Merc 55 or 60 amp alternator can not charge them after playing the stereo all day in a 20 minute ride back to the ramp. Most GM alternators don't charge at idle so when you idle through a no wake zone or you are waiting for the trailer at the ramp you aren't recharging your batteries.

Dago Racing

couple things........my bilge pumps still run with the battery switches off......they are the only thing that runs that I know of too........whatever is draining my batteries is stopping when the switches are off. I had the switches off for a couple days the batteries were fine. I don't know if shutting off the switches would stop the Alternators from draining them if in fact they are the culprit. It rained Saturday so the mechanic didn't come out. Might be out today yet.........we'll see.

hillbilly24

Do you have a VHF in the boat ? If you do here is an easy way to check the diodes. start the engines and let them idle. have someone else listen to another VHF close by. If they hear a whinning sound when you key up you have a bad diode in the alternantor, when the diode fails it alows electrical feedack that wil produce the whinning sound on the radio.

RLW

Hillbilly,
Good Info!

Jerry B

I had an alternator on my Fountain that would drain the batteries pretty quick. Had it rebuilt for allot less than new and works fine . I still shut my batteries off when not in use but if there is a draw, something is wrong. I like knowing everything is working correctly.

CigaretteDon

With everything turned off, disconnect the ground wire on your battery. Now attach a multimeter between the battery ground terminal and the NEG battery cable you just removed. You should only indicate approximately 2-3 volts. Readings at 10+ volts indicate an electrical drain. With the meter still connected, go to your accessory fuse box and remove one fuse at a time - when the voltage drops on the multimeter then you located the source of the drain - Don