Alternator upgrade
 

Hi gang. Last year I upgraded my electrical system from one battery to two deep cycle batteries. Since I did this, I have had problems with the batteries staying charged. My stock alternator only pushes 55 amps. Would an upgrade to a high output alternator cure this problem? If so, how big should I go? I've seen them from 90, 100, 130 and even 140 amps.


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Re: Alternator upgrade
 

That is odd. I have not had any problems with that battery iso system. My alternator is the factory 65 amp. The group 27 handles most all of the electric as the group 29 runs the sound system - two amps totaling 1000RMS. No problems charging and we sit with the stereo going for periods at a time. The batteries seldom read below 70% on the charger when they are first hooked up after going out.

Re: Alternator upgrade
 

Thanks, Moto.

Maybe my alternator is just old and worn out. I've had the boat for three years, so I'm not sure when it was replaced last. There's a good chance it is the original since it is black and the previous owner never did any work to the boat at all. (i.e. the shifter boot was cracked and letting water in the boat. Instead of fixing it, he just left the bilge pump run all the time, lol).
I have noticed the voltage guage bounching around from 10-12 volts when it is idling and would never get over 12 when cruising. I was thinking of going with a larger alternator since I have added a lot of extra stuff on the boat like extra lights, stereo and amp, etc. but not sure how big would be too big

Re: Alternator upgrade
 

You might be able to find that info somewhere out there on the internet. As for your volts while underway I am pretty sure Im running around 14 on the Faria and my Lowrance is reading high 13's. That could be your issue. A buddy turned me onto these DB Electrical alternators. He likes his and it was 1/3 the cost of a Mercruiser part.

Re: Alternator upgrade
 

Thanks Moto,
I'll look into the DB alternators. Mercruiser is mighty proud of their parts!

Re: Alternator upgrade
 

so I ordered a new alternator yesterday. It is a 130 amp, plenty big enough to keep my two batteries charged up and run my lights, stereo, etc. Now do I need to install a larger charge wire? The existing wire (orange, I'm sure is stock factory) looks to be a 8 or 10 gauge

Re: Alternator upgrade
 

You are going to need to at least double the size of the original or parallel it with the same size. Does your boat have a battery isolator? If so, is it rated for 130A?

Re: Alternator upgrade
 

I do have an isolator. I think it is a blueseas unit. I'll have to find out the rating


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Re: Alternator upgrade
 

Blue Seas make nice products. I believe their ML series is capable of 500A , all other series are rated well below 130A.

Re: Alternator upgrade
 

Thanks, Steve for the great info. I will check to see which series I have. Do you think 130 amps is overkill?