Originally Posted by brucemac
how many amps? how much total RMS? i wouldn't mess with your alternator unless absolutely necessary. i'm running 2 amps rated at total 1500W RMS with the stock 03 70A alternator and two optima blue tops and so far it doesn't look like i'm going to need to change my alternator. it would be better, imo, to add a 2nd or possibly 3rd battery and isolator along with a good muli-bank smart charger that you could charge the house bank off the water. good marine grade alternators are pretty expensive. the balmer 150A units that some here run cost over $800.
My stock alternator is just 37 amps. I only had one amp last year and it would run down while it was running. Now I will be running like 900 rms. I got quoted 140 bucks for a 140 amp alternator. Why wouldn't you recommend an alternator change?