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Electrical System Problem

J

jrathsack

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For the last two years I have had an Electrical System Problem.


Every other year I buy a new Marine battery. I bought a new one this year. We go boating for about two hours or so at a time to practice skiing. When we get done boating, I always have to recharge the battery. I’ve had enough of this problem. I desperately need help.

I have taken both the Alternator & Voltage Regulator to a couple auto parts stores in the area to get them tested. They do not have the manuals anymore. “Too old” they say.
I want to purchase the schematic and test procedures for testing the Motorola Alternator & the VR.
I am a technician and can build a test fixture if I knew the testing procedure.

Today I connected a VOM to the battery while boating. It read 13.25v to 13.35v while running 2500-3000 RPM. If I turn on the Bilge Blower, the VOM reading drops to 12.75v. Bilge Blower draws about 4 to 4.25 Amps. The Alternator seems to be putting some energy back into the battery.

How do you test for diode failure in Alternator and a weak or dead VR?
Assuming that the VR is the most likely failure, I called Correct Craft to get a new one. They can’t get any. This is serious.

What is special about an Alternator & VR for Marine use?
Can I replace them both with an Automotive set?
MUST the Voltage Regulator MATCH the Alternator?
The smallest auto alternator I found so far is 60 amps output.
Are Alternators made to turn only one direction? Note Engine is a RH rotation.

I am listing the following specs for the boat & motor and the Motorola parts:
1972 Correct Craft 18 ft Ski Nautique, High-Performance Ski Boat
Mfgs SN: 1998, Motor No. 250-RH (250 HP), 351 cuin Ford (blue engine)
Marine Engine Converter was Crusader
Mfg by Thermo Electron Corp., Model: CO-250 (HP), Spec. RH, Serial No. 81346
Mallory Electronic Ignition

Motorola Alternator
12v Model # M12NCM451, Neg. Gnd., Serial #9582, 35 Amp, Type B
(What does Type B mean?)


Motorola Voltage Regulator (VR)
Model R2CM1 failed. Replaced the VR in 1985 by a thick film type.
Model 8RH20048, Serial No. 23479
Group of three wires: red , black, and green.
One yellow wire goes into the harness. Does it go directly to ignition or thru a resistor to somewhere?
 
I also am keeping old MOT alternators running. Seach the web for the 12v doctors alternator book. If you can't find it, i'll email you a copy. Briefly, the yellow wire goes to the +12v switched source, like coil +. Marine alternators are different mechanically from auto, for safety reasons. Electrically, they can spin either way, the only possible issue is the fan direction. Most MOT's have a bidirectional fan. Does your regulator have an adjustment control on the rear side? It is for the output voltage. Transpo make replacement regulators for these alternators. A good auto electrical shop can rebuild your alt for pretty cheap.

more info: the reg. green wire feeds the field. 0 is no charge, 11v or so is max charge. Black is ground. Red connects to the D+, which is a plus 12v source derived from the alternator. Make sure the red has close to 12v on it when the engine is running.
 
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I agree about the auto electric shop. It is illegal to use an automotive alternator in you boat. It would be a good way to blow yourself up.
 
How about having a good alternator shop rebuild your alternators and make them one wires at the same time? Eliminates a host of problems. You simply wire the alternator's hot post to the heavy wire going from your present regulators to the battery.


Jeff
 
I'd suggest a bit more troubleshooting to isolate the lack of charge to the alternator or the regulator. with a '72 hull, its possible the issue is in the wiring harness, if original.

This may help a bit: http://assets.fluke.com/appnotes/automotive/beatbook.pdf

The "type b" refers to the method used to control the field circuit - one way controls current from the "+" side of the winding, the other controls the "-" side. No real benefit to one over the other but a vital piece of info for troubleshooting.

Don't waste your time at the parts stores; find a good auto electric shop.
 
I searched the Web & easily found the 12v Doctors Alternator book by Edgar J. Beyn.
Is this material a copy of the book? If not, I'll order the book. Also, there was a mention of a
Practical Handbook.

My voltage regulator has no adjustment control anywhere.

Re: Wiring. What does D+ stand for?
Am I safe in saying that the D+ lead from alternator is the feedback loop to the VR?
TNX Diver_Dave
 
My intuition told me that the Marine Alternators and Starters are probably sealed somehow
to keep sparks from setting off an explosion if there are fuel vapors around.
I don't think new alternators & starters have the problem of sparks like the older models.
But I am not taking any chances.
TNX ibnfshn for the "illegal" note.
 
I grabbed the Yellow Pages and called all the Auto Service Shops & Auto Electrical Shops in Central Ohio. Over 20 some. I found two shops that appeared qualified. One of the two shops said we may or may not be able to make it a one wire system. Nobody is open on Sat. (Sad face here.) However, I am making progress (Happy face).
TNX FastJeff & ibnfshn.
 
jrathsack said:
My voltage regulator has no adjustment control anywhere.

Re: Wiring. What does D+ stand for?
Am I safe in saying that the D+ lead from alternator is the feedback loop to the VR?
TNX Diver_Dave
Click to expand...

"D+" means dynamo positive. This means, there is no voltage present until the dynamo (alternator) is running and is putting out current. This is done to eliminate the relay that the old time automotive generator systems used. The yellow wire is used to "tickle" the field into putting out a little bit of current to make the D+ come alive during initial start-up. The regulator adjusts the green (field) wire voltage to put the D+ at 13.6, or so. I'm surprised yours doesn not have an adjustment. If you have a current meter that can handle 35 amps, you can manually jam the field winding to 12volts. When running, the alternator should then put out close to its spec current. In your case, 35 amps. Dont' do this for much over a few seconds to avoid overcharging the battery and make sure all electronics are turned off. If you can't get rated current with max field current, you can use an oscilloscope to view the output waveform. It should have even ripples without high peaks. This is a coarse measure of how good the alternator diodes are. If you can't do these two tests, I'd take it into a auto electric shop and have them put it on a bench. They should be willing to test it for free.
 
Yes, I have the original wiring harness. I don't know where I could even get one.
Would Correct Craft build one for me? I'm sure they don't have those in the parts bin.
I'll try to separate the harness and inspect the wires for fraying and arching.
(Reminds of airplanes with same problems.)

Yes, I was planning on doing more troubleshooting. Now with the "beatbook.pdf" information I have "direction."

TNX for the Type B definition. Nobody has been able to tell me that until now.

Your right, auto parts stores are useless for older items.
TNX makomark
 
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