alternator upgrades
 

this year i added a much larger system than i've ever had before and wanted to get some alternator advice. I'm running a 2000 watt system on the boat, all are class D amplifiers. Jl hd 600.4 bridged to 300w rms to my rev10's, jl jx1000.1 at 900w rms to 2 jl w3's , polk pa2000.2 125w rms to 4 xs650's. My question is will a 70amp alternator be enough to keep up? I have two deep cycle marine batteries from costco, i think group 31 but maybe 27's. Theyre the bigger of the two that costco carries- i know that. I'm thinking i should add a 3rd so i have 2 on my stereo bank and one for starting. I don't have access to 120v at my storage either..

According to your profile you have a 99 Mastercraft. You should be able to upgrade to a Delco 11si that is a 95 amp alternator. It would be a nice little upgrade for not too much money. The 11si is slightly larger than the motorola 8MR style and Delco 7si alternators but not by much. It you have a little room around your alternator it should fit.

What type of pulley/belt does your motor have? Is it a single V belt or a 6 groove serp belt? If it is a single V belt there is no reason to go to anything over 100 amps. A single V belt will squeal and you will burn it up fairly quickly. If it has a serp belt then there are some other options although most good quality stuff is really, really expensive. Like $600+ and that is for just the alternator. With added amps output/draw you will need to make up some custom cables to handle the power.

Your system isn't over the top by any means but if not used correctly with your charging system could result in some problems with short alternator, starter and battery life. To be honest with you I am not sure adding a battery to your stereo bank makes any sense in your situation. Sure you will get longer play time but without a shore charger I am not sure you stand much of a chance to really charging back up a bank that large plus keep your starting battery maintained. If you plan on cove partying while playing the stereo full blast you are pretty much SOL unless you have a serp pulley and/ore willing to spend a grand+ on really upgrading your setup. You can get the Delco 11si for at or under $200 so that is a solid value. The other thing you can do is just know and understand your system. Then you can properly use it and keep the entire package in good working order.

The other thing you could do is add a low voltage disconnect that would shut off your system when it gets to lets say 12.0v or something. Then you would know you need to start the boat up and charge the batteries and when I say that don't turn it on and try and charge a dead battery from an idle. Especially not if you plan on running the stereo while you are doing it.

Anyways, got to go. If you have any questions go ahead. I will try and get back to the forum sometime in the next couple of days and help if I can.

bill thanks for the help... i do have the serp belt, so i'll look into at least the delco11si.. I have a houseboat that i could charge it from as well, but most of the time i do day trips so I was hoping the alternator could help out more. How much do alternator guys usually charge to add windings? Since i just dropped 350 at mastercraft dealership in a pinch when my 50a went, i'd hate to have to dump much more into the darn thing.