Hey Guys I have a 2002 Launch SS with 320HP Indmar engine with stock 7si series GM marine alternator. Currently I am using 3 Optima blue
top Marine batteries with a battery switch, I run 2 batteries all the time on position 1 on switch and have a backup battery on position 2 in case I listen to stereo too long while floating.I have never run the batteries dead by doing this but I did cook my 10si Gm alternator that puts out 100 amps. I have 3 stereo amps total wattage around 1100 watts.I think the 10si series alternator does not cool itself as well as the newer 7si alternator which has a more breathable case and 2 internal cooling fans. So my question is would I be better off with a battery isolater switch that just separates 2 batteries,one for starting and running boat and 2nd battery just feeding amps?? I hear their is a voltage drop when you use a isolator?? Or has anyone upgraded their stock alternator to something that will bolt into existing bracket and still use a single V belt, I understand the newer boats use a 90 amp alternator that uses a serpentine belt, has anyone upgraded to that by replacing all the puleys?? Sounds like that would be costly. I also hear some people use two 6 volt golf cart batteries in series for stereo systems they say it increases your capacity but do they recharge as quickly as a Optima battery?? Going to check out another alternator rebuild shop soon and see what they can come up with maybe a 11si series, I would love to get around 120amps, I may upgrade #10 wire from alternator to starter with #6 wire if I get a new unit over 100amps
Any suggestions would be greatly appreciated I have all winter to sort this out.