ALTERNATOR PROBLEMS?...I THINK

[nuboater]

Ok, here's my new problem....
I went to pick up my boat in Parker and take it for a quick run before going home got it started with one of those portable chargers unhooked the charger and it went dead...this is after I let it run for 20 minutes to charge up the battery. I did it again and started motoring up from the Blue Water and got almost to the buoy's and went to raise my hatch (hydraulic) and it died again...WTF??? I had to maunally open the hatch and hook up the charger again and just went back to the marina and got it on the trailer.
Is this a alternator issue?
Also, when I got the boat out of storage initally I knew the batteries would be dead so I tried to open the hatch with a cable that hooks up to a power port on the boat and connected it to a new battery and got nothing..I had to open it manually this time as well.
any help would be great!!

[1BIGJIM]

Stick a volt meter on the batteries before starting engine. Start the engine and check it again. If it is higher its charging. I would bet it your battery. Have it checked, it could have a short.

[DEL51]

If the diodes short it can pass an ac voltage to the batteries.When checking the voltage use both ac and dc measurements. Ac should be less than 1 volt.Check the connectors and make sure you have a good ground. Try each battery individually,one may have a shorted cell.

[Rexone]

I know this is pretty basic but have seen it many times. Make sure there's water in the battery(s) before charging. If the boat's been in storage many times it evaporates over a period of time (not good for batteries). Also if you've had it on a trickle charger in storage the batteries are likely overcharged and bad. Battery tender type chargers are good, trickle chargers are not...for long term use. In any event you must have water in the battery.

[DUCKY]

You should have between 13.6 and 15.5 volts at the battery when the engine is running.