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.

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

Both batterys run down? or just one?

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.

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

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....

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.

Boat is on the trailer, bilge is dry.

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.

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?