how are you guys powering those big power stereo sys?on a single drive, do they make a dual alt set-up? 4 batteries? i know these systems can pull a ton of amps and was just wondering what everyone is doing. the wife said she wants the water to ripple around the boat when the bass hits

Sounds like my kinda woman..lol

On my single engine boat I have 2 batteries that are dedicated to the sound system with an onboard battery charger, and while on the hook I run a portable generator to power the battery charger. And i have them wired into a battery selector switch so when the boat is running i can switch to the stereo batterys to charge them also from the alternator.

On the twin engine boat i just bought i also have 2 decated batteries for the audio/video equipment and this boat too has an onboard battery charger with a selector switch, BUT i also added a power supply, similer to what a retail store uses on their car audio displays to run all their car stereos. It puts out a constant 13.8v and i have it wired straight to the sound system. But again this only works when the generator is running....

There is NOTHING worse than the batteries going dead after the party really gets started... tends to make the women put their bikini's back on...

multiple batteries dedicated to stereo. you can use an isolator to take the alternator charge & split it between banks (starting batts & stereo batts). the isolator will help protect a bad battery from draining batts in the other banks. also get an onboard charger that can charge multiple banks w/ separate settings.

Now I am just an amatuer. This is what I have researched and learned, but this is not the only way to figure this out.

I calculated the total rms of my component speakers(150watts/speaker x 22 speakers= 3300watts) , convert this to amps and you need minimum of 3300amps of power reserved in a battery bank. Do this also for your subs. This is also providing that your amps will put out at least total 3300amps.
For ex. the standard starting/house battery in a boat is around 800-1200, therefore you would need min. of 3 batteries just to supply the stereo.
How long will this last? It depends on how long the system is putting out max power or half power or meaning full volume or half volume.
Thats where you need a backup, such as a battery charger/generator.
My smaller system would run for about 1hr full power on 2 batteries.

3300 watts does not equal 3300 amps. A 600 watt amp only has a 60-80 amp fuse and should only draw about 40-50 amps max.

I have a Kenwood Class D AMP powering a Kicker L7 12" Sub and a Kicker amp running @ 2 ohm load. Total power is well over 2200 watts. I run all day (8hrs+) @ 3/4 volume on a single battery. (And have an Optima for starting and running.) It isn't a standard battery though.... I bought the largest capacity AGM Battery from the marina. It is almost twice the physical size of an Optima battery. Its hidden deep in my garage, so I don't have the specs.... I do know it is a Deka...and is a true deep cycle, not a dual purpose model (it weighs a freakin ton!!). My standard alternator won't put a dent in this battery, it requires an overnight charge @ 10amps to bring it back after a full day of use. I am planning on adding a second (duplicate) battery this spring on a switch and also keep my Optima strictly for starting and running.

The biggest thing is you need deep cycle batteries!!!!!!!!!!! I run 4 deep cycle together(2 banks). When they go dead a jumper pack is very handy. It will run easy 8 hr.@3/4 volume and usually start the boat. total 4500+ watts

I have 1000 watts RMS (PDX digital amps)and can easily run 4+ hours on my one Interstate Group 29M Deep cycle that is dedicated to the stereo. Actaully, I have never run it all the way down.

i haven't had alot of luck with the optima batterys. would a couple of standard group 27 or 29 deep cycle work ok? just a 4 bank on board charger work? most of those are usually like 10amp chargers i think. is that enough? how big are your generators?

ok i am going crazy looking at amps . i have a loud boat so i need my sounds to be loud. i have two big batterys and 100amp alternanor . . i have a sony cd player bose speakers and 700watt amp i like to put two speakers in the back with a amp that with work for me . now i read some amp get hot and some need 14.2 volts drain a lot of power ??? so should i just take this out of the boat and start over with new stuff????