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Discussion Starter · #1 ·
Last week’s installment of the stupid tax was a blown alternator due to reverse polarity. It was dark- don’t ask. Anyway in good boating fashion I’m going to pretend I wanted to upgrade it anyway and replace the original 30 year old 60 amp unit with a 105 amp kit from Catalina Direct.

What’s the downside? Energy is never free, those extra amps are generated somewhere.


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Unless the new alternator is designed that much more efficiently (not likely) you will lose some horsepower to generating power. According to Google (I didn't vet the source) an alternator uses 1 HP per 25 Amps. So at full output I guess you will lose about 2 HP. Based on the articles on Mainsails website, a basic alternator is probably heat limited and will therefore not be at full output for very long.
 

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bell ringer
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The downside is $$$$$$$$$$$$ and time.

And the upside may be minor to nothing depending on your batteries and how you use your batteries. I have a 100 amp alternator than I have belt program reduced it to 80amp as the amount of time my 464AH battery bank would accept 100A is so short as to be meaningless. So unless your batteries could normally accept more amps for a meaningful amount of time there isn't much to be gained. Since I have solar it is rare that I run engine just to charge the batteries.

How much battery capacity, how low do you normally allow them to get, how long do you normally motor at a time, do you normally run engine just to charge your batteries?
 

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You need to balance the size/capacity if the components.

How many HP is the engine?
How many AH are the batteries?
How many amps do you draw in a day or between "charging" from whatever source?
How long do you run your engine typically to recharge (and whatever)?
 

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One of None
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I'll let you know the boat I'm buying has a 105 on the yanmar 24 horsepower but first thoughts are you need a wiring upgrade at least from the alternator to the charging components but unless you have really really bad connections and really bad even worse batteries it's not likely it ever runs at full amps anyhow. Per Mainsail if you have a universal diesel that's older and has an amp meter you have a fire hazard already. We did the wiring change upgrade on my universal 16 horsepower just before I sold it it was not a difficult job, new meters new ignition switch with key on the wires from the panel to the engine
 

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Money wasted if it isn't needed.

All the other stuff that needs upgrading in order to use it safely & effectively.
 

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Last week’s installment of the stupid tax was a blown alternator due to reverse polarity. It was dark- don’t ask. Anyway in good boating fashion I’m going to pretend I wanted to upgrade it anyway and replace the original 30 year old 60 amp unit with a 105 amp kit from Catalina Direct.

What’s the downside? Energy is never free, those extra amps are generated somewhere.


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We really need to know more about use and the battery bank.

I would not suggest purchasing the 105A alt from CD. It is a cheap knock-off of an actual Leece-Neville and we see them burned up or failed with quite high regularity.

If you want to stick with internal regulation, not really all that optimal, then a genuine Leece-Neville 8MR2401UA (Sales # 110-567) is the unit you'd want. The problem with anything over about 80A is you will have belt dusting issues. This is why external regulation (Balmar or Wakespeed) is such a big factor as it allows you to dial back the amps so the belt can survive.

There are a LOT of sleazy dealers out there so be 100% sure you are getting a genuine Leece-Neville alternator from a legitimate Leece-Neville dealer. Expect to pay about $250.00 for the bare alternator. Any less and it is likely a clone masquerading with phony LN part numbers.

If you are going to spend that money buy a quality Leece-Neville, not a knock-off unit that won't last. Best option is to convert to external regulation while you're in there. A CMI-105-ER (the only availble externally regulated 8MR on the market) would allow you to do this.
 

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Keep in mind that a) that alternater will only put out the full 105A if it's running fast enough ... I have a 100A on my boat and it usually only puts out 10-30 amps. Another thing that will throttle it are the batteries ... the batteries have to be able to accept 105a or the charge controller will throttle it back. It won't hurt anything, but it's a waste of $$$ unless all the pieces are in place to allow it to operate at full capacity ... I mean, if you have LiFePo batteries and a way to drive the alternator at optimal RPM, then great! Otherwise, you'll probably wish you'd spent the money elsewhere.
 

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Bill, if you have the W50, the single 3/8" belt won't drive it. I have a Balmar, too. I believe the original alternator for the W50 was 55A. Can't get a serpentine belt kit for the W50, but if you have the W40, GET IT.
 

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Bill, if you have the W50, the single 3/8" belt won't drive it. I have a Balmar, too. I believe the original alternator for the W50 was 55A. Can't get a serpentine belt kit for the W50, but if you have the W40, GET IT.
I have to be honest, all things considered, I don't remember the details of what I have. But I can say that I remember carefully researching it and making sure that belt could drive it. I also don't have any evidence that the belt was ever an issue. I think it just came down to the solar panels working so well that there wasn't any reason for it to power up in most cases.
It's another good point for the OP, though. Gotta have a drive belt that's rated for whatever the alternator needs or you'll have trouble if it ever does try to crank out the full 105 amps.
 

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Pay attention to what Mainesail said in post #7. Great advice. And read his the articles he posted the links to. Best upgrade is to go to an external regulator.
 

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Discussion Starter · #12 ·
Great info here, thanks for all the reply’s. Sounds like I need to do more research to figure out what’s best. Truthfully we only use the boat on weekends now and the solar more then charges the batteries during the week so we rarely run the motor just to charge the batteries under normal circumstances. It may not be worth the trouble of upgrading.

Any suggestions for where to get a straight replacement alternator with external regulator?


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OK, I'll be even more specific. Go to Mainesail's website (link in post #7) and then to his Webstore. Lots of alternators with external regulators there for very competitive prices. Call or email them for technical help. They are great.
 

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Discussion Starter · #16 ·
OK, I'll be even more specific. Go to Mainesail's website (link in post #7) and then to his Webstore. Lots of alternators with external regulators there for very competitive prices. Call or email them for technical help. They are great.
Thanks! I will check it out.


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My diesel mechanic (the town’s favorite) warned that too large an alternator would strain the motor, slow the engine’s RPM’s and reduce boat speed. Another issue limiting alternator output is ambient heat of the engine space so consider adding ventilation fans on both the air-in-and-air-out sides of the compartment. I would be VERY suspicious of any 90-100 amp alternator that costs less than $700 before installation. Adequate gauge cables are critical as well and add protective silicon end caps at all connections.
 

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Not a likely issue, but my alternator was upgraded by a previous owner. It now bumps into the exhaust pipe when rotated to change the belt. It now requires a longer belt that can't be tightened optimally.
 

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Last week’s installment of the stupid tax was a blown alternator due to reverse polarity. It was dark- don’t ask. Anyway in good boating fashion I’m going to pretend I wanted to upgrade it anyway and replace the original 30 year old 60 amp unit with a 105 amp kit from Catalina Direct.

What’s the downside? Energy is never free, those extra amps are generated somewhere.


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The engine may strain and sound odd at lower rpm because of draw. I know a guy with that situation that could not understand why his engine was running rough at start and low speed. He went back to standard alternator which solved that problem. Just something to consider.
 

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A good regulator lets you limit the amps.

Or a DC-DC controller does the same.

However you do it, the alt does not pull HP unless high current is being pulled.

A kill switch to remove power from the ignition wire which powers the regulator located at the helm

will allow all power to go to propulsion when needed
 
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