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Generator Choices

Your old Chris-Craft electrical system can be a challenge. If it runs on "juice" pose your questions and offer your advice here.

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Moosemeat
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Generator Choices

Post by Moosemeat » Tue Jun 17, 2014 9:55 pm

I am in the process of changing over to a 12 volt ignition system for my '47 Sportsman. A clubmate sold me a late fifties two brush 12 volt generator, which I am having rebuilt. However, a knowledgeable boat mechanic tells me I would be better off with a modified three brush generator. The three brush unit would supposedly produce fewer voltage/ amperage spikes.
I can't help thinking that the generator that was built to produce 12 volts would be the best bet, along with a voltage regulator which I have, than a modified unit.
I am planning to use a Pertronics distributor.
Any advice as to which way to go?

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drrot
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Re: Generator Choices

Post by drrot » Wed Jun 18, 2014 7:49 am

I'd go with the factory 12 volt.
Jim Staib
www.finewoodboats.com


1947 Penn Yan 12' Cartopper WXH474611
1950 Chris-Craft 22' Sportsman U-22-1532
1957 Chris-Craft 26' Sea Skiff SK-26-515
1968 Century 17' Resorter FG-68-174

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evansjw44
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Re: Generator Choices

Post by evansjw44 » Wed Jun 18, 2014 8:18 am

Use the two brush generator with an appropriate regulator. The three brush generator is ment to operate with only a cut-out and has very little regulation.
Jim Evans

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Re: Generator Choices

Post by Moosemeat » Wed Jun 25, 2014 9:19 am

Thanks for the advice guys! I just got the two brush unit back from its spa treatment, installed it and its new regulator, and it runs fine. The gauge say its giving me about 20 amps at 2100 rpm which is about what the 6v system did.

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parroteyes
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Re: Generator Choices

Post by parroteyes » Thu Jun 26, 2014 5:35 am

20 amps @ 6 volts is 120 watts.
20 amps @ 12 volts is 240 watts.

Sounds like you've doubled your power.
Hull # 16-R-OX2 (March 1946)
Engine 1B #26564

That's me 1950 - already a CC lover!

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evansjw44
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Re: Generator Choices

Post by evansjw44 » Thu Jun 26, 2014 9:45 am

Regulators are supposed to bring the battery up to "Float" voltage and carry the system load and then back off the current keep from overcharging the battery. I would connect a reliable voltmeter to your battery and check to see the regulator is holding the battery voltage at not higher than 14.4 - 14.6 volts. I suspect with 20 amps ouput you are over charging.

Now, when you see 20 amps on the ammeter (assuming in the posetive or charge direction), we must look at how it is connected. Normally, the ammeter is connected such that it only measure the current to and from the battery. The 20 amps would then be current headed to the battery and unless your battery is in undercharged condition that's a lot. The current the generator is supplying to the ignition, lights etc is not measured.

However, if your ammeter is connected such that it is measuring the output of the generator then perhaps the 20 amps is more reasonable. This is not the traditional connection for an older CC electrical system. (It is for alternators on CC V8s) One test you can perform easily is to turn the key on and observer the ammeter deflection with the engine not running. It should indicate in the negative or discharge direction.
Jim Evans

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Re: Generator Choices

Post by Moosemeat » Fri Jul 18, 2014 9:04 am

Now that I have been able to run the boat at speed for a longer time, I see that it is doing what Jim said it should; that is it charges at 10 (not 20) amps for a while, then cuts the charge down after about 40 minutes of operation.
What a difference 12 volts makes! A boat that starts without a fuss: woo hoo indeed!

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