How the heck do I get a bigger alt on here?

[alctel]

Engine is a Isuzu 54HP 4LE2 with a 50 amp alt on it. I've converted it to external regulated and added a wakespeed reg while I try to figure out how to get a bigger alternator on. Wiring was all redone with 2/0 etc.

My plan was to either get a 240amp Balmer and run it at 200 or a 200 amp one and run it at 150. Either way, I need to use a serpentine belt - and that's the issue.

The current system uses two V belts, one drives one water pump, the other drives the alternator and the other water pump. Because of this, I can't just replace the pully with a serpentine one.

The only idea I've had is bolt the serpentine pully onto the front of the existing one, move the new alternator forward and then add a free spinning tensing wheel for the pump (as it's fixed in place) - then I would have three belts, the 2 V belts each driving just one pump and the third serpentine belt driving the alternator. I have 3 inches in front of the engine so I think I could make it fit.

Anyone else had a similar setup they made work or any good ideas how to do it? Also, who do I talk to to get a custom Serpentine pully made anyway? I talked to my usual machine shop and they don't do them.

[wholybee]

Balmar has a selection of pulleys. None specifically for your engine, but perhaps one is close enough it could be made to work by drilling new bolt holes? What is the pump to the left? That would be the most difficult thing to deal with. Ideally the new belt would drive that as well.

[Jammer]

That's tough. I wouldn't do it. Could easily turn into a $2500 project.

One thing I would suggest is adding an idler pulley to the existing alternator V belt to get better belt wrap around the pulley. I think that would help a good deal. Do that, use a premium belt, use the field limiting feature in the regulator, and you could have a reasonably solid setup.


You could replace all four pulleys and use a serpentine setup, again with a well-placed idler to get good belt wrap. The pulleys would likely have to be custom made.

[glenn.225]

This may be a solution, but it does involve some planning, parts scrounging and machining.
A number of years ago, I rebuilt a jeep engine and wanted to add an A/C pump for an air compressor and a large frame alt for emergency welding.
What I did was take the front pulley (harmonic balancer) and turn it down smooth, cutting the v grove off. Then, I found a large diameter serpentine idler pulley and turned it to tightly fit over the crank pulley. Added a few tack welds so it wouldn't move and then modified the brackets to accept the accessories. Installed the serpentine belt and a spring tensioner, and it has worked ever since.

[Statistical]

You should be able to do 100A without switching to serpentine. I would do that and spend the money saved on more solar and a steak dinner.

[alctel]

Thanks for the suggestions everyone - as to using a single v belt, apparently a 1/2" really maxes out at 85amps according to
https://marinehowto.com/marine-alter...n-tips-tricks/

[SailingHarmonie]

Originally Posted by alctel

Thanks for the suggestions everyone - as to using a single v belt, apparently a 1/2" really maxes out at 85amps according to
https://marinehowto.com/marine-alter...n-tips-tricks/

I easily run a 24V 50A alternator on a 3/8 v-belt. That's the same amount of power as a 12V 100A unit.

Is it a perfect solution? No. You really have to stay on top of belt tension, and belts last about 400 hours or so. But it works and has for 27 years and 9000 engine hours.

If you can't tension a belt or change one yourself, you might want to be more conservative, but if you know which end of a wrench to hold it works fine.

[alctel]

Hmm, I'll look into it, thanks. Might be worth giving it a crack, although I hope I can use 1/2" belts

[s/v Jedi]

Why can’t you change to a serpentine for the main belt? Just buy the conversion kit with pulleys for crankshaft, coolant pump and alternator, then bolt the extra pulley for water pump">raw water pump back on.

[Bowdrie]

Looking at the pics, it looks like the degrees of belt wrap on the existing alternator is not enough to support 150>200 amps even with a Multi-rib belt?
Yes, serpentine belts are nice, but they are still a friction drive and do require high tension.
The less belt wrap the higher the tension required.
You can, (to a extent,) reduce belt wrap by going to a wider belt or a larger pully on the alternator, both of which add surface area.
Adding surface area in the system is, (generally,) always preferable to adding tension, no matter the belt configuration.
Sometimes a bearing supply/power transmission shop can help you.

[wholybee]

Originally Posted by Bowdrie

Looking at the pics, it looks like the degrees of belt wrap on the existing alternator is not enough to support 150>200 amps even with a Multi-rib belt?
Yes, serpentine belts are nice, but they are still a friction drive and do require high tension.
The less belt wrap the higher the tension required.
You can, (to a extent,) reduce belt wrap by going to a wider belt or a larger pully on the alternator, both of which add surface area.
Adding surface area in the system is, (generally,) always preferable to adding tension, no matter the belt configuration.
Sometimes a bearing supply/power transmission shop can help you.

Converting to a serpentine belt would involve adding idler and tensioner pulleys on the outside to increase wrap.

[hlev00]

Out of curiosity, what are you planning on charging with this larger alternator? Have you worked out your electrical AHr budget? The suggestion of solar is a good one if you have space and depending on how you plan to cruise.