Generator questions

[mike n]

Hello.i want to put a generator on my 1963 evinrude 40hp.i have 2 generators laying around.one is a prestolite gjg 4008m that has the bracket and bolts up perfectly.the other is an auto lite gjg 4003-m with a smaller pulley.can I swap pulleys if I need to?what is the part number for the belt?is there a way to bench test these generators.thanks

mn

[frankr]

There are only two pulleys, one is for twin cylinder motors, other is for V-4 motors. Twin is the larger one of the two. It is used with a top flange to keep the belt on.
Don’t pay the absurd price for a belt from OMC/BRP. Go here instead: http://shop.polybelt.com/255L037-Black- … egoryId=-1

To bench test a generator:
1. Ground the field terminal (the small one) to the case.
2. Connect a jumper wire from a 12V battery neg (-) to the gen case. Use at least a 16 GA wire
3. Connect another jumper wire from pos (+) to the armature terminal on the gen (large one) Use at least 16 GA
Generator should run slowly like a motor. This proves that generator is working right now. It doesn’t prove it isn’t worn out and may conk out tomorrow. An inspection is required for that.

[chris-p]

I have had a couple rebuilt by a starter repair shop, fairly cheap, as I didn’t have the parts nor the knowledge to do it.

If you cross polarize the battery cables by mistake, you will need to re polarize the generator. TO do this, jump the ARM post on the regulator, to the BAT post on the regulator, but DO NOT TOUCH THE FLD post or you will damage the regulator.

Fairly easy to test when installed with a voltmeter at the battery. Your battery at rest should read about 12.65 volts.

When running the motor, above 3500 RPMS, the voltmeter should read between the 12.65 volts and about 15 volts. Your ammeter on your panel will be around 10 amps, and should decrease as the voltage climbs. Anything other than this needs further troubleshooting. We can get to that if need be.

[frankr]

Bench testing as I described earlier automatically polarizes it correctly. I suppose somebody could reverse it if they are careless.

[mike n]

Thanks I will try that tomorrow.are the two generators the same? Can the pulleys be swapped if one generator isn’t working.thanks for the link on the belt.

mn

[frankr]

I gotta confess I don’t know what the difference is between those models. I thought they were all the same. But there might be a difference that I don’t remember. I suspect it is merely a matter of the era it was built. If it fits, use it.

[mike n]

I tested both generators as you said and they both spin. I took one apart to check it out. The brushes look ok and I cleaned them off. The bearings feel slightly rough. Is that normal. Can you get these bearings from a bearing place like boca bearings

mn

[frankr]

As far as I know, they are common standard bearings. That thing spins mighty fast, much faster than the 4500 engine RPM, so you want decent bearings.

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