Battery Drain? HELP!
 

A buddy of mine in Ft Lauderdale has a battery drain on his twin outboard boat.

He's had it for years and this just started. Of course he bought two new batteries and they went dead within days so it's a drain for sure.

What should he look for and where?

I told him to isolate it by unplugging one fuse at a time but he said that's not really possible.

Should he just torch it??? (it's a fishing boat) or try to fix it before he looses all of his hair?

Thanks.

Re: Battery Drain? HELP!
 

You can take off the gournd wire, get a test light and put it btwn the negative term. on the battery and the ground wire. If it lights up you have a drain. Is it possible that his bilge pump is stuck on running? I have seen that a couple times. If the light is on he can just disconnect curcuits tell the light goes out.

Jon

Re: Battery Drain? HELP!
 

Both batterys run down? or just one?

Re: Battery Drain? HELP!
 

Lots of places could cause a drain. Alternator with a bad diode will suck power, radio amplifiers, bilge pumps, interior lights left on during the day so no one sees them etc. Connect a volt meter between the neg battery post and the wire. if it reads the same as connected across the batery, the drain is present. A light like Audio said will work but only at higher drain levers(approx 1/4 amp) will be a dull glow, hard to see in daylight. If a meter across pos and neg posts shows 12v and a meter between neg post and neg cable( disconnected from battery) shows same reading, start disconnecting circuits one at a time until meter drops below battery voltage reading.

Re: Battery Drain? HELP!
 

Yup, both batteries that start the engines run dead within days of charging.

Re: Battery Drain? HELP!
 

Any standing water in the bilge that may have a wire in it? I've had a float switch where the wires were so old, they were like dirt inside the insulation, and actually drew power......looked fine from the outside...He can use a multimeter on the neg terminal and see how many amps are being drawn....

Re: Battery Drain? HELP!
 

I'm assumming he has battery switches and that they are both turned off when he is not using the boat... If this is the case, look towards the bilge pumps / bilge pump auto switches. Also look at anything connected to the batteries that bypass the switches.

Re: Battery Drain? HELP!
 

Boat is on the trailer, bilge is dry.

Re: Battery Drain? HELP!
 

I take it he is not hearing the bilge motor run. Switch can get stuck & motor keep on running even when bilge is dry.

For both batterys to run down then either both batterys are tied together or two different things are draning the batterys. If there is a battery switch then it might be in the "BOTH" position. That would explain why both batterys are going dead.

As stated above it could be any number of things draining the batterys. I had a power amp that went bad & would not shut down. Only took a day to run the battery down.

Re: Battery Drain? HELP!
 

Sorry I am no expert here but I had a bad iso box that was causing both of my batteries to drain. Could possibly be that?

Re: Battery Drain? HELP!
 

I would do what Audiofn said he hit it on the head. pull one fuse at a time until the light goes out . At least if you look at a wiring dia, you will know what is on it.

Re: Battery Drain? HELP!
 

I've been sending my buddy your posts. It's a 22' cat hull with two 40hp yamaha. The cat pontoons are filled with foam. The boat is self bailing and doesn't even have a bilge pump. :eek:

Re: Battery Drain? HELP!
 

Where/what is an ISO box?

Re: Battery Drain? HELP!
 

Maybe you left your headlights on :evilb: :D

Re: Battery Drain? HELP!
 

It is blue box should have three bolt at the top, finned like an amp. Only about 8inches long, this was the problem on my boat and I know I don't have half the experience of these other guys. I do know you don't really need them though because we took mine off and I never had a problem again. It is used I guess to equally distribute power to each battery from the alternator but can go bad and cause the batteries to drain from my understanding.

Re: Battery Drain? HELP!
 

Ron, tell him to disconnect the main engine harness plugs one at a time and check with a meter or light as previously described. My bet is a bad diode in the charging rectifier.

Re: Battery Drain? HELP!
 

Both Motors? or both batterys are tied together & 1 bad diode is running both batterys down. Anything is possible.

I would make sure both batterys are not tied together. Then he will be able to figure out what side the problem is on.

Re: Battery Drain? HELP!
 

This is a great way to check.. Also if you turn your meter to amperage, and connect the meter from the neg. wire to the neg post this will show you how many amps you are drawing.. If your meter has that resolution.... But I agree with Airpacker.. Also insure that your battery switch is not on both batteries. This places the batteries in parrallel and drains them both.. Great for recharging but bad when you have a problem..

Re: Battery Drain? HELP!
 

TJ, I suspect both batteries are tied together and one motor is the culprit. Of course, he could have had a bad battery originally which caused one charging system to take a dump and create the shorted diode or boosted it backwards and fried the rectifier on one or both motors? Can't tell without testing ya know :)