alternator problem, 24ssv

[mpiller]

Hey guys, just took the boat out yesterday (2007 24ssv) and both of the batteries were dead. I replaced one with a new battery, but had my buddy hook it up and he said the first time he had the wires wrong, but fixed it. Boat ran fine for a while and I left it running most of the time in order to charge the dead battery. Well about 3 hours in I noticed The voltage was at about 10 volts, and the motor began to skip/miss a little bit and then died. Now the battery only had enough power to operate the bilge pump, but couldn't start the motor. I had to get it towed back after that. I'm guessing the battery got drained because the alternator wasn't working. The radio didn't work so I figured it was just connected to the dead battery and would work once it got charged back up. We did use the auxiliary 12v plugs for air pumps and ballast pumps quite a bit. My question now is that is there a fuse or breaker before the alternator? Or do I need to just check the alternator's output and replace it if it needs it? The boat had not been having any problems before hand, so Im wondering if my buddy tripped a fuse or breaker by hooking up the battery wrong.
Thanks

[Zim]

Before you do anything else, pull the batteries out of the boat and stick them on a battery charger to see if you can get a full charge. If you left the batteries in your boat throughout the winter, you very well could have ruined them due to cold weather and not being on a trickle charge over the winter.

Once you've charged the batteries up, put a voltometer on the terminals and see if you're getting 12v. Now put the batteries back in the boat, and if you have a perk switch, switch that to the "all" option or "both" whatever it says. Start your boat up, preferably on the trailer if you have a fake a lake. Use the voltometer to check the voltage at the battery terminals while the boats running. While running, you should see around 13.3 volts. If that checks out, now give the boat a little throttle and watch what happens to the voltage at the battery terminals. It should raise up to a max of about 14.4V. Any higher than that (15-16V range) and your voltage regulator on your alternator is shot. If you see no increase with more throttle, your alternator may be shot.

First things first though, confirm your batteries are charged, and in good working order.

[mpiller]

Awesome I appreciate it, I'll try to do that today. As soon as we got off the lake I put the batteries on the charger, the first one (new one) charged up fine but I haven't checked it with a voltmeter, but the battery charger said it was charged up fully. Stuck the other on the charger last night and haven't had a chance to check it yet. If the voltage regulator on the alternator is shot will the alternator still be ok or can I just replace the voltage regulator? And if I don't see an increase in voltage with more throttle does that automatically mean the alternator is shot or is there a fuse before the alternator that could blow?
Thankyou

[Zim]

Awesome I appreciate it, I'll try to do that today. As soon as we got off the lake I put the batteries on the charger, the first one (new one) charged up fine but I haven't checked it with a voltmeter, but the battery charger said it was charged up fully. Stuck the other on the charger last night and haven't had a chance to check it yet. If the voltage regulator on the alternator is shot will the alternator still be ok or can I just replace the voltage regulator? And if I don't see an increase in voltage with more throttle does that automatically mean the alternator is shot or is there a fuse before the alternator that could blow?
Thankyou

If there's a fuse between the alternator and your battery, then I don't know about it. I just had to replace my alternator this year due to a bad voltage regulator. The regulators are not separate from the alternators, so you'll need a new one if that's the case. Also, don't have it rebuilt, because once you crack the case it's no longer sealed for marine applications. My new alternator ran about 180 bucks from a local alternator shop. Yours is a 90amp as opposed to my 70 amp, but that shouldn't matter much.

Check the voltage with the boat running, that'll give you a good idea what to check next.

[michael hunter]

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NEW INDMAR MARINE ALTERNATOR 8600002, 20827 11SI 95 AMP

[mpiller]

Just checked everything out, both batteries had 12 volts before hooking them up to the boat and also once they were hooked up. Once the motor was started the new battery stayed at 13.14 and the old battery stayed around 12.24. Under about quarter throttle the newer battery never increased above 13.5 and the other battery never got above 13 volts. Guessing I need a new alternator? Thanks for the help and the eBay link. How hard was it to replace the alternator? I've done a few trucks before, just never a boat alternator.

[Zim]

Just checked everything out, both batteries had 12 volts before hooking them up to the boat and also once they were hooked up. Once the motor was started the new battery stayed at 13.14 and the old battery stayed around 12.24. Under about quarter throttle the newer battery never increased above 13.5 and the other battery never got above 13 volts. Guessing I need a new alternator? Thanks for the help and the eBay link. How hard was it to replace the alternator? I've done a few trucks before, just never a boat alternator.

Doesn't seem like you need a new alternator with those voltages. If it wasn't charging, you wouldn't see anything above 12 volts. When you see the voltage in the 13's that means you're getting a charge. Try going for a water test and take a jump box with you if you have one (or just hook up 1 of your batteries and bring a pair of jumper cables). You may have just had 2 completely dead batteries before. If that's the case, the alternator won't help them, as alternators aren't designed to charge a battery from "no charge" to a full charge.

[michael hunter]

Remove the battery's trickle charge them over night and have them tested.

[CJD]

The alt sounds good to me.

I bet the problem was you hooked a dead battery to a fully charged one. That drew down both batteries, and then they never had the chance to fully charge. A fully charged battery will show at least 12.6 volts...using a real voltmeter...not the "that's about right" meter in the boat instrument panel.

Your new battery sounds good. The old battery, with 12.24 volts following a full charge, is on its death rattle. I would not count on it, and would separate it from the good battery when not charging.

[mpiller]

Okay that could make sense, since the good battery was bought new this past saturday. I just hooked it up so I could start the motor and figured while out riding the dead one would charge up but y'all are saying that could have drained the new battery causing both to die? I'd rather spend $90 on a new battery vs $90 on an alternator considering the battery is a 2 minute switch. So to test, y'all think I should take it on the lake and then test the batteries out once it's under more throttle? Luckily I'm in a housing community with a small lake I can put the boat in for shorter periods of time.
Thanks guys