Low Volts batteries wonbt seem to charge

"I've got a new boat, dual

"I've got a new boat, dual selector switch, it appears that the CO2 detector was hardwired and was constantly draining the batteries. I disconntected this, however after running the boat for 8 hours last weekend when I got back to dock to flush the engine the batteries wouldn't start as there was not enough juice in the batts. Could it be that the batteries need to be fully recharged as I have only jump started the batteries since they were dead or could it be the alternator not working properly? It's a 2004 5.7 penta and I would think that if the alternator were not working properly then the engine would eventually stop running once the batteries wore out? Any ideas would be helpful.

thanks"

got a volt meter?

got a volt meter?

"Hi Dhogencamp. Like Scott sai

"Hi Dhogencamp. Like Scott said. Get a volt meter and check the voltage at the batteies with the motor running. It should be between 13 and 14 volts, if not they are not charging. Next step bad connections or have the alternator tested."

"If your battery voltage is to

"If your battery voltage is to low to excite the alternator it will not charge. Use a volt meter to check battery level. If there is more than 10 volts (12VDC system) it should work. If not, use another battery to excite the alternator by hooking it up in parallel to the start battery. Most boats will have a parallel switch for this reason. If this is OK, check the ignition wire to the field on the alternator. It should have power when the key is turned on. If you have an “external” regulator check that the switch wire (usually brown if standard) from the ignition has power when ignition is turned on. On an “external” regulator if you have power on the brown wire check that there is power (1 to 12.7 or so) on the blue field wire coming from the regulator to the alternator. Some regulators have a 45 second delay before the blue wire is powered up.
If you have power on the following test and no out put the regulator may be bad. Again with an external regulator, un-plug the wire harness from regulator and jump the red wire to the blue wire with an alligator clip while the engine is running. This will by-pass the regulator and excite the alternator.(Do not let it run like this for more time than is required for the test as it will over charge the batteries and turn off all voltage sensitive equipment like radios and navigation instruments first) If you still have no output the alternator is faulty. This could just be diodes. (Usually blown diodes are caused from switching batteries or disconnecting the battery when while the engine is running). It could also be the internal regulator if so equipped. If all this checks out and the batteries are not taking a charge and all of the connections are good, then you will need to load test the batteries. For this you will need to borrow or rent the proper testing equipment or take the batteries to a shop that can do it for you. Some testers if done on the boat can tell you the performance of the alternator i.e; diodes or low amp out-put. Nigel Calder’s book has a great section on alternators and batteries I highly recommend it. Good luck"