alternator problem, 24ssv

[CJD]

That would be my bet.

To put it in perspective...a typical battery will have about 130 amp hours. Lets say the new battery was charged, but the old was down by a full 130 amp hour drain. Now, with a 90 amp alternator, you would still have to charge over an hour (130/90 hours), with no other load, for the dead battery to charge fully. Add to that the extra time needed for the loads you put on it. And, when the batteries were hooked up reversed, you also ate quite a few of the amp hours on the new battery.

So, it could be something else...but I would bet it was just low batteries and not enough time to charge them.

[Swamplandkarl]

If you un hook the battery while the motor is running and it dies you prolly need a new alt...if it stays running you prolly have a bad battery...

[mpiller]

Ok so I was in a hurry earlier and believe I may have had the digital multimeter on the wrong setting. Just rechecked the batteries again and the older one put out 12.75 volts without the motor running or anything drawing on it. The new battery put out 13.14 volts again so it looks like my older battery should be fine? Gonna try to put the boat in the lake in a bit and start the motor and see what results I get this time. Basically from my understanding the alternator should be fine if the batteries jump to a little over 14 volts once the motor is running? Really hoping this could have just been from the other battery being dead last Saturday.
Thanks guys

[Zim]

Ok so I was in a hurry earlier and believe I may have had the digital multimeter on the wrong setting. Just rechecked the batteries again and the older one put out 12.75 volts without the motor running or anything drawing on it. The new battery put out 13.14 volts again so it looks like my older battery should be fine? Gonna try to put the boat in the lake in a bit and start the motor and see what results I get this time. Basically from my understanding the alternator should be fine if the batteries jump to a little over 14 volts once the motor is running? Really hoping this could have just been from the other battery being dead last Saturday.
Thanks guys

You can always take the battery to an auto parts store and have them load test it. That will tell you if your batteries are good, and it's free.

[mpiller]

I'll give that a shot tomorrow with the older battery. Unfortunately we had some tornado warnings and bad weather come through so I didn't get the boat out tonight but should be able to tomorrow morning and hopefully get some better readings on the volt meter.

[CJD]

The batteries are not capable of 13.14 volts on their own without being on a charger...or within a handful of seconds after removing a charger. Your voltmeter is off. You can interpulate the high battery from 13.14 down to the max it could be of 12.69v...and that would still put your old battery at an actual 12.3v. That's still on a death rattle for a charged battery. But, if you separate it when not being charged and use it as a secondary battery for the stereo, you could still get a season out of it...maybe.

[mpiller]

Just took it out today, before start up I got the same 13.14 and 12.75 volts on the batteries. Before ever contacting either terminal the volt meter read about .60-.80 volts so I'm guessing it's off. Upon starting the engine the batteries stayed exactly the same, never above 13.14 or 12.75, also under throttle the batteries never moved up at all. Thinking I'll go ahead and order that new alternator and get a new battery too.
Thanks for the help guys

[mpiller]

Quick question about my perko switch, both batteries are the same neither are a deep cycle. When selecting which battery to use on the perko switch, each battery should be able to do everything right? Say I choose battery 2, it should be able to play the stereo along with start the motor, but battery number one should be able to do the same also? Today when starting the boat nothing would work on battery 2 as if it were completely dead even though it showed 12.75 volts, flipped the switch to all and everything worked fine. Completely forgot to check if it would work on battery 1. But if I understand correctly the common on the perko switch sends power to the starter and everything else, both batteries had a charge and each battery had a positive cable running to the perko. The ground is run to one battery and sends a jumper to the other. What could be causing number 2 on the perko not to work and could this be related to my problem? I'm really just learning to use the perko correctly, luckily last summer I never had any troubles.