Battery Or Alt. ????

I was out on the lake for the first time today and had an issue. I was out driving my 86 SN 351 stock boat and the battery went out. I had drove it around for 30 mins, swam, and drove around for 15 mins. then parked it at the boat dock and backed the truck in. after walking back to the boat it would not start (5 mins after parked). then the boat ramp got full and someone gave me there battery. started right up. Now I would like to know where you would start on this fix. The batt is 6 years old and alt was rebuilt 3 years ago. Now the batt was total drained by the radio and re-charged before using the boat.

THanks for any input. (other then grammer and spelling errors... hahahha)

brett

I agree with Bill. Six years on a battery is pushing it a little. The radio probably finished it off. When you get it running again,try putting a meter on the cables at the battery. You should see 14 to 15 volts above idle with some acc. on. If not,get the alt. tested.

thanks all... that is what i was thinking... now... do i do the 2 batt set-up since i have been planning it?...

Thanks! All... I had planned on getting a new battery but did not want to have the same issue next time....

I agree with the last post. I would check the charging system first. Here is a real simple check: Disconnect the battery and pull it out of the boat. If you have access to a battery charger. Charge the battery. With a volt meter measure the voltage at the battery. It should be about 12V. Reconnect the battery. Start the boat. Check the voltage at the battery again. It should be about 13.5-14 Volts. If it is then the battery is bad. If it is not then you have a charging system issue.

Took the battery to Auto-zone... and I was told it is OK. So... next it to pull the alt and have it checked.

Now... if that is bad... what is going to take to step the Alt up to 55-75amps over the stock 35a?

brettmcox wrote: Took the battery to Auto-zone... and I was told it is OK. So... next it to pull the alt and have it checked. Now... if that is bad... what is going to take to step the Alt up to 55-75amps over the stock 35a?

Well you can do that all you want but the part that needs tested will still be on the motor as it's an external regulator and that's what's wrong, I'm sure Autozone is going to tell you it's (alt) is all right, since they won't even get it hooked up right to test it since it's not wired like a car's.

79nautique wrote: test the thing your self just get a volt meter, start the boat and read the voltage at the battery and if you have 13.25-14 volts then it's charging and the batteries shot, if it is less or more than that then the regulator is bad.

and if your going to chime in about 12-13 volts being good read the link in detail because your wrong, yes you know who I'm talking to. testing a battery

brettmcox wrote: Took the alt to Auto Zone and they tested by putting in some box thing, putting on a belt, and pluging in the power and ground but did not have anything on the A.C. plug. Total Fail.    got an order for a new one....

that doesn't suprise me, just up grade to an internal regulated alternator. If you want you can just try replacing the regulator mounted on the rear of the motor with your current alternator and you might luck out and be able to save some money.

An '86 should have already had an internally regulated alt. PCM made the change mid year '83.

one other item... when I had the Alt tested... the AC (exciter wire) was not going to anything.. i looked on google and found this...
"I'm getting a low voltage, I think it's because there's no exciter wire hooked up to the alternator."
"All you need is a wire hot with the key in the on position and no power with the key in the off position"
any input here.... or should i just stop asking "?"s