View Full Version : Alternator upgrade?

05-14-2005, 02:54 PM
I'm in the process of adding a stereo to my '85 S&S, and the original Motorola 35A alternator just won't do. Anyone have any suggestions on where to get a replacement and what a good brand is? Looking for at least a 70A alt. For now, I may just add a head unit and speakers, but plan to add a couple amps and a sub eventually.

05-14-2005, 03:25 PM
try ski dim. if they dont have one they at least can give yoyu suggestions.

05-16-2005, 08:06 AM
Look in your phone bbok for an alternator/starter rebuilding shop. They should be able to build you a high amp single wire marine grade delco for about 80$.

05-17-2005, 11:52 PM
I agree w/ scrambler...... Find a local alternator/generator shop in the phone book to build you a brand new one. I replaced mine w/ one that runs something like 240 watts of power through it for around 90 dollars. It has no problem running a 12" sub w/ an 800 watt amp and four 6 1/2 tower speakers on a 550 watt amp.... also a light bar! The upgrade is well worth the money.... my voltage meter would wiggle a little when the sub hit hard on my old alternator but stays solid in one spot w/ my upgrade! When you do your sub woofer and all your other speakers and head unit I would also suggest adding a second battery to your boat! You can buy a switch at a marine store or auto parts store to switch between the batteries for around 30 dollars. Having a high output alt. will help keep juice running to both of those. Not to mention it is nice to be able to kick back for a while and listen to some tunes w/ your buds & suds and when your done the boat will actually crank! Happy Boating! :cool:

05-18-2005, 12:23 AM
dsuthy190; Did you mean 240 amps? I think normally the stock alternators are around 60 amps X 12 volts or around 720 watts?

Engine Nut
05-18-2005, 08:41 AM
Make sure to use a marine alternator and also make sure to increase the size of the wiring from the alternator to the starter and from the alternator to ground. The existing wiring is not able to pass the extra current from a higher output alternator.

Engine Nut

05-18-2005, 07:41 PM
Thanks for the info guys; found a local guy who can build me a delco unit with Marine upgrade kit for about $100. He says it will put out about 63amps. What amperage are you guys running?

05-18-2005, 08:16 PM
Alternator on my 2001 LTR is 51 amps. I think MC went to a larger one the next year due to all the electronics, speakers, etc. Engine Nut is right, when I inquired about the higher capacity alternator when mine needed a warranty replacement, the dealer said the harness would have to be changed to handle the higher output, and that was as much as a new alternator.

07-19-2005, 03:20 PM
Does anyone have any idea what the existing wiring in a 2000 or 2001 Mastercraft is capable of handling. My 51AMP alternator died and I got a 70AMP replacement. Do I need to change the wiring? or is the jump from 51 to 70 not enough?