Replacing Alternators with more Power

[bigralph]

One of my alternators on my 1990 F32 w 350 Crusaders crapped out. I'm replacing both with new 100 Amp alternators (original 51A) from a local rebuild guy. He provides a 1 year warranty and has a great reputation. So, I looked at the original owner's manual and took a bunch of pictures and I'm still not entirely certain how I want to rewire her. A PO (anyone else naturally want to add an 'S' at the end of that acronym?) painted everything on the engine when he repainted a few years before I bought her. I believe the gummed up painted wiring is 12 AWG and I'm going to replace with 4 AWG. There is a small (32 A) breaker on the engine block before the solenoid. It looks like I need to replace all the wiring to the solenoid and the battery terminal with 4 AWG. That's easy money. The problem I'm having is deciding on the breaker. Anyone else have experience with this? Where did you get the breaker?

[Paul]

I'm guessing by your post that you know how to correctly size the wire based on the current carried over a specific distance. What you might not realize is that the horsepower required to drive this alternator upgrade at 100A is pushing the limits of a single V-belt. If you already have a dual belt or serpentine set up, then no problem. If not I'd recommend upgrading the belt set as well.

Where you'll notice a problem with the single V-belt is after spending some time on the hook with your refrigerator, stereo, etc running for some time off of the batteries. When you start the engine to head off, the alternator will want to throw allot of amperage at the batteries to catch up again which puts a heavy strain on the belt. If you look at the floor in your bilge under the alternator and see a black rubber dust stripe, you'll know the cause.

Hope this helps,

[bigralph]

How hard is it to add a second pulley? That seems like a lot of work, but I'm electric by nature, not mechanical.

[Big D]

You'll also want to check with the battery manufacturer or do some research on what the max charge amperage should be for your batteries/banks. It's one thing to push 100 amps to a large battery, it's entirely different pushing that much through a 24 series battery if it's low enough to require a full charge. If it's a big enough bank then no problem but you must consider this or you'll kill your batteries quicker. You'll find for example that some good battery charger manufacturers will recommend outputs based on battery or bank size.

I'm guessing by your post that you know how to correctly size the wire based on the current carried over a specific distance....

+1
Must carry full rated output plus a safety margin in case of a component failure.

[BobCT]

I wouldn't do it, I looked into this as well. When your at the dock, it really doesn't make a difference how long it takes for the batteries to recharge. On the hook, the only way this helps you is if you run the engines but they have to be a lot higher than idle speed.

Underway, I don't think I've ever needed the batteries to recharge faster. I guess if you ran them down and then made a short trip on the hook again it might help. Between the pulleys, wiring and cost of the alternators, I gave up on this upgrade. My original intent was to run an engine while using the inverter and offset some of the load.

I think the ones I replaced the original 50 amp ones with were slightly higher at 60 or 65 amps.

Bob

[mikeandanne]

I would have to agree with some of the above---- a good 50 amp alternator will probably get you 30 amps true output at best----- now if most twin engine boats like ours have 55 amp alts and they function fine to recharge two or three batteries--- then I believe two 100 amp alts are overkill and maybe creating a new list of issues unless everything is resized accordingly--- We don't have all the power accessories top line autos have to run while driving---- all we do is recharge and run some very low draw stuff---- Just my two cents---- Mike

[Commissionpoint]

It may seem like a good idea to upgrade alternator output, espescially on the house side, but as mentiond by a few of the guys above you have to be careful and consider several issues so you come out with an acceptable finished product.

I don't like the idea of simply rewinding an old alt to put out a higher amperage. If higher amperage is what you truly desire, look into a reputable manufacturer like Balmar. http://www.balmar.net/6-series.html A 70 amp 6 series is likely a much better solution than trying to upgrade your old case to a higher amperage with new internals. Balmars have a nice output at lower RPM's than your standard factory alt.

[rbcool]

+1 on all above!
I wouldn't see a need for anything above 65-70 amps unless you're running ALOT of 12v stuff while underway. My charter boat friends run the big alts because they are running massive electronics, including twin radar, couple of fridge's, pumps,major lighting, etc.
RB
(but hey... my wife said I didn't need a 42' flat screen in the galley either)

[ready123]

Were it me and wanting to charge multiple banks while underway I would spend the money on a remote multi stage regulator and get the shop to bypass the internal regulator and supply the output tap from the alternator!

[prowlersfish]

The problem with these hopped up alternators its the don't have the cooling capacity to take the hi load for long and at a 100 amps a single Belt is over loaded . most these alternators live a short life.

I recommend going with 70 amp (or less ) that stays within the limits of what a single belt can handle and the cooling capacity of it . A internal reg is fine and trouble free

If you need a 100 amp unit ,you need to go with a large frame alternator not cheap and many are not approved your use with marine Gas engines and of course making one fit can be fun

[Paul]

I recommend going with 70 amp (or less ) that stays within the limits of what a single belt can handle and the cooling capacity of it . A internal reg is fine and trouble free

I have a single belt 70A alternator charging a 230Ah house bank and cranking battery thru a 70A isolator. I often drain my house bank down to 50-60 % and this set up has no problem charging the bank while under way, even while the refrigerator and other DC loads are operating. The system seems fairly well balanced and belt life is not an issue. I tried doing this with my original 1 wire GM alternator, which was around 35A, and it started smoking. Had to shut off all loads while charging under way.

[bigralph]

I didn't realize the thread was still active, bc I stopped getting update emails. Sorry.

So, lots of good input. My thoughts are that the alternator is just a device, like any other generator/alternator and it's only going to put out the current demanded. I don't plan to ever draw more than 50% of my battery and if I did, it would be an extenuating circumstance and the cost of a belt wouldn't be my biggest concern. I also have a genny onboard and can always use the battery charger if I pull too much on the hook. Also, everything on the engine is still protected by the factory 50 Amp breaker from the alternator to distributor cap. The only unprotected lead is the battery and coil and there should never be an open between a running alternator and a battery, from my limited 12 VDC knowledge.

My original post might have came across wrong - this isn't a rebuilt, this is a new belmar that was sold by a car alt guy and he added a spark arrestor and changed the foot on them so that it mounts to my Crusader 350.

The drawing in the Crusader owner's manual is a little misleading about the output wire from the alternator to the coil. It shows the alternator feeding into the coil and 2 other loads on the coil in parallel. The reality is that the factory electrician used a single lug and 3 10 AWG conducotrs fed into this lug, 2 of which are the other 2 connections on the factory OEM manual. (Personally hate this way of wiring).

I cut the factory orange wire from the lug on the coil and replaced the orange lead with a new 4AWG marine silver tinned conductor with a new lug on top of the old one with the 2 remaining leads.

My rewire project was further complicated by a PO (POS) repainting the engine block and in order to paint, he wrapped all of the wiring in electrical tape then spray painted the hell out of the tape. It took more time to get the elctrical tape off than anyting else.

Anyway, my battery was a little lower than I like last night when I started her up and she purred like a kitten. I was so proud of myself.

Then she purred so hard that she wouldn't shut off. That's right, somewhere another gremlin has surfaced and my ignition switch doesn't work. 2 Folks have told me that think it s a coincidence, but I don't believe in coincidences. I think I either fried something in the coil or the switch. So, there will be another update in the future.

Anwyay, so far one engine done, one to go.

[Paul]

Then she purred so hard that she wouldn't shut off. That's right, somewhere another gremlin has surfaced and my ignition switch doesn't work. 2 Folks have told me that think it s a coincidence, but I don't believe in coincidences. I think I either fried something in the coil or the switch. So, there will be another update in the future.

Anwyay, so far one engine done, one to go.

Makes me wonder if your alternator is feeding power directly to the coil thru your reconfigured wiring. This would render the switch ineffective once the engine is running.

Might be worth looking at.

Paul

[prowlersfish]

Then she purred so hard that she wouldn't shut off. That's right, somewhere another gremlin has surfaced and my ignition switch doesn't work. 2 Folks have told me that think it s a coincidence, but I don't believe in coincidences. I think I either fried something in the coil or the switch. So, there will be another update in the future.

Anwyay, so far one engine done, one to go.

Makes me wonder if your alternator is feeding power directly to the coil thru your reconfigured wiring. This would render the switch ineffective once the engine is running.

Might be worth looking at.

Paul

I agree seen it happen before , the feed from the switch to the alt is wired incorrectly .

Paul (#2)

[mikeandanne]

I think that wire going to the coil is the 12 volt feed for the alt field which is probably about 2 amps as there is a resistor--- now if that has been shorted somehow it will put 12 to the coil instead of from it if you follow me--- don't know how these new alts excite --- but I believe that is how the original was----hope this helps--- Mike