65 Amp Alternator Capacity

I've got a 51 amp Prestolite/Leece-Neville alternator at the moment that has some problems (Lots of rust, bent fan, etc) but still charges. I'm planning on replacing it because I don't trust it and will be going on a short vacation at a lake with the boat next month. I don't want the alternator to mess up our plans.

I'm currently running an old 200 watt HiFonics amp and the factory 35x4 head unit and have had no problems with the 51 amp keeping up.

Long term I may go to a dual battery setup w/ isolator so I don't have to worry about draining my cranking battery. I may also go to a 5 channel amp and add a 10" subwoofer but nothing expensive. I have no plans to ever spend more than $800 or so on a "system".

The boat is an '00 MasterCraft Maristar 230 VRS with the Indmar LTR. The mounting bracket restricts my ability to jump way up in capacity without somewhat major surgery on the bracket. There's no room for additional case diameter.

My cheapest replacement option at the moment is a 65 amp direct replacement at $71. Based on my above "hopes and dreams" should the 65 amp be sufficient?

I have the option to go to a 90 amp in the same diameter case but it's double the price @ $152. I'd have to put a heavier charging wire in but would this be worth it/necessary?

I talked with a local rebuilder and he said it wouldn't be worth reworking mine given the physical condition and the case is too small for adding much extra amperage.

Since you're on a budget, how about db electrical? I believe they make a 125 amp alternator in the same case for around $80. I've never had a problem with my 165a unit from them.

Originally Posted by wotan

Since you're on a budget, how about db electrical?

That's where I'm looking. The guy I talked to there said that it's just expensive to build the alternators in that small diameter prestolite case with much amperage. Which one are you referring to specifically?

It looks like a Delco 10si "style" 105 amp replacement from DB Electrical for $57:
http://www.dbelectrical.com/p-3610-n...o-adr0106.aspx

The price is great but I'm unsure if it will be a bolt on or if I will have to "massage" my bracket. The holes are supposedly the same as my current alternator but I'm unsure how the diameter of the case will play out on my bracket. The sure thing is to get the 65 or 90 amp direct replacements but they are both more money for less output (The 90 amp at $152 being a lot more $$$ for less output).

Thanks for the link on the DB electric, looks like a good price for a lot of amps. Do you know if they will always charge while key on/engine running? My current alternator is annoying in that you have to rev the engine a fair amount, like 1500+ RPM before it'll start charging. I never cared for those goofy Chevy style self exciting jobbies for that reason.

Anything over 105 amp expect to pay alot more than $100 for. If a company is selling them bigger, ie 135/165 in the same casing they are using very cheap parts and most of the time wont' can't put out the state amperage. go to a reputable shop and have one of those db electrical alts tested and gone thru. I got laughed out of my local guys shop. This was years ago when I was running a much larger system and kept burning up those db alts. I know some people have had decent luck with them. People in the business will tell you they are made with very cheap, unreliable chinnese parts.

Keep in mind that just about anything over 100 amps needs dual belts or a serpantine belt. You will have slippage or really short belt life with a higher amp unit and a single v belt. In addition to get that high of output out of those small frame alternators they usually have screw with the idle output. You may be getting nothing at a 650 rpm idle. The alternator might not even turn on till you get up to 800-100 engine rpm. In that case the only time they put out anywhere near the rated amperage is when they are spinning really fast.