Which Alternator Installation

(iroc) · (iroc) **Join Date: Mar 2006** 04-07-2006, 6:18 AM

I am trying to upgrade my current 51 Amp alternator to my 2001 Mastercraft X-Star. I went to the local part store and found nothing close to the one that is on the boat. It has a 5.7L GM Engine in it. Has anyone upgraded there alternator to a bigger Amp rating ie. 105,130,140Amp. Do I need to order one from Mastercraft, or can someone help me on one from a local part store. Thanks for any help. Joe

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 04-07-2006, 6:40 AM

Local alt people should be able to help you, take it to an alternator repair shop they should be able to rebuild it up to around 90-105 amps.

(3205lpv) · (3205lpv) **Join Date: Nov 2005** 04-07-2006, 6:41 AM

You can not order from an automotive store. It has to be marine rated for shock protection. That way is there is any fumes of gas in the bilge your boat won't blow up.

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 04-07-2006, 6:47 AM

most alt. shop will be able to recognize that it is marine, if they don't go somewher else. But it's alwasy good to mention it to them

(sjmedic) · (sjmedic) **Join Date: May 2004** 04-07-2006, 6:51 AM

Just had mine done, went from 70 amps to 125. Had the guy bench test it for me right there, and sure enough 125. A smaller pulley will increase output, and going to 10 guage wire will increase the output as well. Dual setups are also an option. The guy charged me 180 bones, and he made sure it is still marine safe.

(fox) · (fox) **Join Date: Jul 2002** 04-07-2006, 8:04 AM

Do you need to upgrade the wiring/fuses in your boat to handle this upgrade? I would like to get a little more out of mine, say 51amp to 70-90amp, but I'm a little worried about cooking everything. AS it is, at night with lights, auto bilge, and stereo the voltage meter really drops and the lights are really dim. I want to add an amp and sub to my system and LED's too so I think it's impossible given the current set up.

Eric

(iroc) · (iroc) **Join Date: Mar 2006** 04-07-2006, 8:10 AM

Thanks for all the input. I will check my local Alt shop here, small town they might not have one. Thanks again. Joe

(sound_illusions)

Eric-putting LEDs in your boat will not draw very much power, a system in your boat couldnt or couldnt draw alot of power. If you plan on keeping your install to a minimum then you will be ok with the setup that you have. Just because your alternator is small doesnt mean that you are not getting the output that you need. This is the reason for the battery. The battery acts like a shock obsorber in your charging system. The alt gives the battery juice and the battery takes the hit when your boats electrical system needs it. If you plan on adding batteries and going with a big sytem then I would look into getting your alternator rewound.

(sound_illusions)

Eric-putting LEDs in your boat will not draw very much power, a system in your boat could or couldnt draw alot of power. If you plan on keeping your install to a minimum then you will be ok with the setup that you have. Just because your alternator is small doesnt mean that you are not getting the output that you need. This is the reason for the battery. The battery acts like a shock obsorber in your charging system. The alt gives the battery juice and the battery takes the hit when your boats electrical system needs it. If you plan on adding batteries and going with a big sytem then I would look into getting your alternator rewound.

(fox) · (fox) **Join Date: Jul 2002** 04-07-2006, 8:58 AM

Thanks Clayton. What is not up to snuff in my electrical system that it can't run the motor...nav lights...auto bilge...and a simple clarion deck without causing the voltmeter to drop to like 10?

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 04-07-2006, 9:19 AM

Eric How do you knwo yoru alt is 51 amps? HAve you had it bench tested? I had a 96 prostar and I think the alt was only like 30-40 amps. Have you tested the voltage at various points in your electrical system? My exp is most boat guage voltmeters aren't very accurate. you may have some corroded connections causing even more voltage drop??

(cyclonecj) · (cyclonecj) **Join Date: Jul 2001** 04-07-2006, 11:26 AM

Eric, A faulty battery caused my boat to do just what you describe. It would charge up but wouldn't hold a charge under load, and was pulling down the alternator output. Replacing the batt = 13.4 vdc all the time. Have your batt(s) load tested.

(fox) · (fox) **Join Date: Jul 2002** 04-08-2006, 6:30 AM

That is a good idea psyclone. I had an older battery which did the same thing. I replaced it with an optima blue top, and it still does it. I am wondering if the voltage gauge is bad/inaccurate?

Adam, the alt has been replaced with a model purchased from SKIDIM and is the 51amp direct replacement. It could be underperforming...I just don't know.

(yosquire) · (yosquire) **Join Date: Jun 2005** 04-08-2006, 7:07 AM

Eric,

What happens when you fully charge your batteries at home, then kick on your accessories, do the lights still dim? If so, then your alternator is not the problem. You're looking a bad-connection or insufficient wire size problem.

I took an alternator to an actual Alternator/Starter shop yesterday. They were able to load test it. It delivered only 75% of it's rating while charging at 12.6v.