1996 Mercury 2 stroke 75 Charging, what batteries to run with a 600w stereo

Hello, I am new to the site but hope someone can help me out. I have a 20 foot Fisher pontoon with a 75 horse 2 stroke mercury outboard. I run a deep cycle 12 volt to run the motor and use 2 6 volt golf cart batteries connected together to make a giant 12 volt to run the stereo and accessories. The 6v batteries will last a good 18 hours with all the accessories and 600 watt amp stereo system. The only problem is i have to plug it in to my battery charger every 14-16 hours of use to charge. The deep cycle is the only battery hooked to the motor and it's charging system. Do you think I can run an isolator to charge up the deep cycle and then have it switch to the 6v batteries or will this create too much of a demand on the motors charging system trying to fill those huge batteries constantly. I also thought about yanking the deep cycle and running everything and the motor on the 2 6 volt batteries but again am afraid of hurting the motor's charging system. I don't even know how many amps the motor puts to the batteries and since it only has a pos and neg cable to the battery, I don't know how to hook it and the batteries up to the isolator. Anybody have any ideas???
Thanks in advance
Eric
jerseysmail@aol.com

Re: 1996 Mercury 2 stroke 75 Charging, what batteries to run with a 600w stereo

You can buy a bigger deep cycle battery if charge is the problem........or You can get a solar charger to help maintain.......Even running a trolling motor I charge my batteries after every time on the water......welcome to the battery world man...not much you can do about them dying....