high output alternator?
 

has anyone installed a h.o. alternator? i have a 70amp stock unit currently but would like to get a 125 or 150 amp unit. i have a 2200 watt stereo system and dual blue top optimas. i would like to put a better recharge into them while the engine is on. let me know what you have done? thanks!

i bought a 200 amp alternator from powermaxxusa on ebay for $160. has worked well

You might check these guys out too. I had them build a HO alternator for my snow plow truck.
http://www.excessiveamperage.com/

I have a delco 7si that came with the mercruiser, and never had luck finding anything HO for that alternator. Even local shops can't upgrade it.

Do you have the ability to plug a shor charger in at night? If so you are better off buying a 20 amp+ 2 bank charger and adding/replacing your batteries with bigger/better batteries.

Anything 200 amps for $160 is a complete POS. Balmar is the only one I know of that makes a good quality high output alternator in a small frame and since you have the mercruiser with the dual lower foot mount it isn't going to be as easy as just swapping an alternator. You could use a Balmar 6 series 150 amp alternator but you will have to mod/fab the bracket some as the options for that alternator are a 1" spool mount, 2" spool mount(1" with an adapter to make it 2") and a dual foot J180 style mount but the spacin isn't the same as the Delco 7 si that comes on the mercruisers.

Oh yeah, the Balmar 6 series is somewhere in the 700-800 dollar range for just the alternator. Keep in mind if you up the amperage much you are going to need to upgrade or add to your battery cables.

yeah...i went to an alternator/starter shop that said he can't make my alternator any better because of the small case size of it. he did say he could build me a 125 amp unit that is one size case larger using all new parts(he showed me around his shop)for around 240 bucks and that i would have to modify my mounts/brackets to make it fit. and yes i saw the balmar units. price prevents me from that. i find it hard to believe that with all these boats with big ass booming stereo systems that there isn't more availability for an alternator upgrade from the stock units. that being said, what is the real difference between an auto and marine alternator? if i could find a direct bolt in unit from a car with 125-150 amps i would seriously consider it.

Jeff, basically marine units have enclosed brushes/brush holders so thtere is no chance of spark and igniting gasoline fumes. In a Diesel appliction it doesn't matter but in a gasoline application you bet it does. If he is building something up for $240 it is almost garunteed to be a chinese clone and using cheap parts. Doesn't mean it wont work, but the chances of failure are greater. IT also might not perform as you expect. The problem is a lot/most people with huge stereo's sit with the boat off while playing the stereo loud. A big alternator doesn't do you much good at that point. Also, most of the aternators that are smaller and say they are 100+ amps have terrible low rpm output.