dead batteries...help

This has been a most frusterating and continuous problem on my 99 air nautique for about 3 years. My boat constantly drained batteries for the past 2+ years and it was getting really old, I figured that it was the alternator because the volt meter constantly charged at 16. when I took it to the dealer they said that the alternator tested fine and the voltmeter was reading high. They did not have any in stock, so they couldn't swap it out they said.

This past month I installed a new stereo that was quite demanding and in an effort to beat the battery draining problem I put in two blue top optimas and a 150 amp alternator from the battery shack. I tightened the belt like Grant and others had said to do, but it was charging at nearly 17 volts....a little worried I loosened the belt a little trying to get the voltmeter to read at a reasonable number. that ended up being too loose and it smoked the belt. I bought a new belt and put it on just like I have any other belt before and sure enought the voltmeter reads 16-17 and almost 18 when running wide open. I began to think that the dealership was right and the voltmeter was reading high....

but a week later I started getting dead batteries again...I am lost. There is nothing runnning in the boat. The ignition is off and still after sitting for three days the batteries are dead. If I put them on a trickle charger they will last for about 4 days. then I put the boat in the water and NOTHING...it tries to start but the batteries don't have enough to turn it over.

Does anyone have any ideas???

Hey Rich, I am only a novice at all this boat electrical stuff, but I had a problem with my friend's boat and did alot of research on the subject. Our problem was a blown alternator and a questionable stereo wiring job on a 92 sport. We simply had to replace the alternator, get a new head unit, and wire it into the accessory panel off the ignition.

In my limited knowledge, it sounds to me like you have a short in your system that is draining your batts even when the boat is shut down. I am not sure what kind of 2 battery setup you have, I am thinking you have an isolator, that is your ignition and house load batteries are separated and cannot drain from each other. There may also be a switch that allows you to charge either battery, both batteries, or none.

I am of the impression that you have either a short in your electrical system, or your isolator and/or battery switch is messed up. You may also want to check that all your main connections are secured and cleaned, especially the ground, which should run to the engine block.

Unfortunately, I am not familiar with your boats battery setup, and maybe you could post some more info on how you have your stereo, isolator, and batteries set up. The fact that both batteries drain and won't recharge may mean a simple fix, but there may be a short some place that is completely draining off your batteries when running the boat.

When you say four days, is that running the boat?? Or is it sitting on the trailer and you come back to it??

Did the dealer check the electrical system??

i saw a deal at boat us or west marine that claims it will prevent that kind of thing. will be going back over there in later today and i will find out the name of it.

Not sure if this related - but years a ago I read an article about boats that are on lifts with battery draining problems. I really do not understand why this works, although I feel like I have good understanding of circuit loops, but the problem was that when the boat was lifted some part of the drive (this was I/O article, but guess would apply to inboard) remained in the water.

Since the battery grounds to the block, and there is a metal to metal connection throughout the drivetrain the battery was effectively grounded to the water. No big deal when you are out running around but over time would allow the battery to drain.

Like I said this did not make sense to me, but I have had similar problems with my boat and started raising the lower unit when on the lift and sure enough it holds a charge now.

882001
I saw the same kind of thingie, it's like a switch that prevents battery drain when the ignition is off, basically, when the battery (starter?) get's to 12 volts, it cuts it off until the ignition goes. Could be a simple solution to the problem.

Richard:

I am a bit confused as to exactly what the problem is. There are two conditions, which would have entirely different solutions.

Condition 1: You start with a reasonably charged battery, but over the course of a few days (with the boat being run every day) the battery ends up dead.

Condition 2: The battery starts off somewhat charged, at least enough to start the boat the first time on the weekend. You run all weekend with no problems. You put the boat away, but then the following weekend the battery is too dead to start the engine again.

If you are suffering from condition 1 then the alternator is not providing enough output to keep up with the demand. Either install a larger alternator or turn down the stereo (or don't runt the stereo with the engine off)!

If you are suffering from Condition 2 then something is drawing power when the boat is "off". I am not sure about the 99 Nautique, but the 2001 Nautique that I used to own had bilge pumps that turned on for a second every few minutes, and the keyless ingition took a fair amount of power. It would take a month or more to drain my batteries. I installed a battery switch to completely turn off the battery when I wasn't using the boat.

Another possibility is that your amps aren't powering down like they are supposed to. There should be a "power on" wire from the Stereo to the Amps that powers them up only when the stereo is on. This wire doesn't provide the power, just an on/off signal so it is a fairly small sized wire. If the stereo didn't have a suitable output, or if the installer was lazy, the amps may have just been wired to be always on, which would draw a fair amount of power. Most amps have an LED that is lit when the amp is powered on. If this LED stays on when the stereo is off then this is likely to be your problem.

My first recommendation to you is to get a multi-meter, preferably one that will measure 10 amps or so. Start by taking a voltage reading right across the battrey when the engine is running 2000 RPM or more. If the voltage is more than 14.2 volts then it is too high and it will destroy the battery fairly quickly.

Next, turn everything off. Disconnect one lead from the battery. Set the multi-meter to AMPS (the RED lead usually need to plug into a different socket on the meter). Connect the meter between the empty battery post and the wire that belongs there (it doesn't really matter which lead goes where).

In a perfect world you would read 0.000 amps. This world we live in isn't perfect so it should read something. 0.010 amps is trivial, the battery would last over a year. If it reads 0.100 then I would expect the battery to last a month or so. A reading any higher than that and I would expect you to have trouble.

Whatever you were attempting to do with the alternator belt was certainly the wrong thing! The belt needs to be properly tightened. If the alternator is putting out too much voltage then the regulator is bad and needs to be replaced.

Rod