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Voltage Regulator for 12 Volt Conversion

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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Riviera Wish
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Voltage Regulator for 12 Volt Conversion

Post by Riviera Wish » Fri Nov 04, 2016 2:27 pm

Would like to get some information and suggestions for the conversion of a 1952 Riviera 'K' engine from 6 volts to 12 volts.
Existing 6 volt generator has a single wire out put through a relay that only allows the generator to connect to the battery when charging output is sufficient. Question: what prevents overcharging of the battery or 'frying' the battery?
I have read that conversion to a 12 volt generator may require a voltage regulator, that if mounted on wood, would require a ground wire. Questions:
Would this voltage regulator control the generator output by controlling the field current as in an automotive application?
Would an automotive regulator work to control the generator charge rate?
Would (could) the 12 volt generator conversion have a field coil terminal (existing 6 volt generator does not)?
If there is only a relay in the 12 volt generator's output connection, what prevents overcharging the battery?
What are good sources for 12 volt generators and compatible voltage regulators?
Seems to me that a 12 volt generator with an automotive type voltage regulator (controls field current) is the best conversion approach. Please reply with your suggestions and comments.

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Re: Voltage Regulator for 12 Volt Conversion

Post by tkhersom » Fri Nov 11, 2016 6:18 am

Hi Steve:

I am not ignoring you, I just don't have the answers to your questions. I think you are going to have to find a professional electrical guy for this one.
Troy in ANE - President CCABC

1957 CC 21' Continental "Yorktown" (Mom's boat)
1958 CC 38' Connie "American Beauty"
1985 Formula 242LS "Gottago"
1991 Formula 36PC "Band Aids"

Life Is Too Short To Own An Ugly Boat

Riviera Wish
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Re: Voltage Regulator for 12 Volt Conversion

Post by Riviera Wish » Fri Nov 11, 2016 1:10 pm

Thanks Troy. I have inquired with a friend who has done the 12 volt conversion but can not remember the details; he is checking his notes, and boat. Many owners have made this conversion and must know the answers to my questions; I am awaiting their replies. Will continue to independently research the problem and will post any findings.

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Re: Voltage Regulator for 12 Volt Conversion

Post by drrot » Fri Nov 11, 2016 1:53 pm

The original third brush 6 volt generators charges by RPM. They don't over charge (generally) because they have low output. Maybe 8 amps. Same is true if you convert to 12 volt and keep it third brush. After 1956 Chris-Craft used a 12 volt generator with two wires coming out of it. That regulator senses voltage and charges when the battery needs it if there is sufficient RPM. They are also low amps.
Best conversion is an alternator. They charge at idle. Pat at Crussen Classics makes one that fits right on.
Jim Staib

1929 Chris-Craft 26' #898
1929 Chris-Craft 28' #3107
1947 Penn Yan 12' Cartopper WXH474611
1950 Chris-Craft 22' Sportsman U-22-1532
1959 Chris-Craft 26' Sea Skiff SK-26-515
1968 Century 17' Resorter FG-68-174

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Re: Voltage Regulator for 12 Volt Conversion

Post by joanroy » Fri Nov 11, 2016 1:59 pm

I have a 1948 W engine with an early 6 to 12 volt conversion set up. It does have a separate voltage regulator mounted to wood. The regulator has a ground wire to the block. I'd talk to an engine restorer about getting the correct parts for you conversion.

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Re: Voltage Regulator for 12 Volt Conversion

Post by evansjw44 » Fri Nov 11, 2016 4:31 pm

I should have answered earlier but now is the time. The 6 volt generator is a "third brush". That means the generator field gets its current from a third brush that contacts the armature commutator from a differrent location around the commutator than the power brushes that feed the electrical system. The field gets less than full voltage and thus regulates the generator output voltage. Essentally, the generator output voltage is directly proportional to its rotational speed but the battery clamps the voltage to its terminal viltage thus once connected to the battery (via the cut-out) the output current is directly related to the rotational speed (engine RPM). This is pretty primative stuff. CC used these on many if not all conversionn engines until 1955 orn 1956. Late 30s and early 50s cars had some externally regulated generators instead of third brush generators.

In around 1957 CC changed to a 12 volt system and used generators with an external voltage regulator. The result is the external regulator could maintain the generator output voltage reasonably constant over a wider range engine RPMs. This provided more power and better charging at low RPM as well as protection from overcharging.

Now you have a third brush generator and to get to a 12 volt system you must adopt an externally regulated generator. I suppose you could actually make field coils that would make your 6 volt third brush generator operate at 12 volts but you would need some special field coils to do that. I'm sure that it is easier to find an externally regulated generator that will mechanically fit your engine. As for connections you need: a wire from the battery (ammeter) to the BAT terminnal of the regulator, a wire from the the ARM terninal of the regulator to the ARM terminal of the generator (these should be heavier guage wires, normally #8 AWG), a wire from the FLD terminal of the regulator to the FLD terminal of the generator (#14 AWG is sufficient), and a wire from the case of the regulator or GND terminal to the engine block ground. Note that the GND terminal of the generator connects to the engine block via it's mounting bolts (there actually isn't one but one exists functionally).

After making all the connections it may be necessary to "flash" the generator fields. This is done by connecting the battery terminal positive to the generator FLD terminal momentarily.

Consider looking for a "Genernator" replacement if you can find one mechanically compatible. A "Genernator" is an alterntor (like in your car or modern marine engine) stuffed into a case that is physically similar to your generator but has modern internals. It is a "one wire" device and needs only a connection to the battery (ammeter). They have high output and good regulation.
Jim Evans

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Re: Voltage Regulator for 12 Volt Conversion

Post by Riviera Wish » Tue Nov 15, 2016 1:27 pm

Thank you all for the great advice and information. I just got off the phone with Pat at Crussen Classics; nice guy. He sells an alternator that bolts-up to the 'K' engine for $529. Uses the same bolts and drive belt. The alternator is internally regulated with one wire output that charges at low RPM. I plan to use this alternator for my conversion. The 12 volt power will also solve the problem of power to a bilge pump since 6 volt bilge pumps are like 'hen's teeth'. Incidentally, the alternator also increases safety since it is spark proof however it is not clear if it will pass the scrutiny of all judges.
Thanks again for all the help and insight.

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