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Old alternator and no wire diagram

briang0

Regular Contributor
The alternator on my Chevy BB died and I have to replace it. The engine is a 1964 Crusader CS280 which is a 409ci. The alternator I took of has the following model number Motorola M12NCM55G. It is a 40amp 12 v negative ground 1 wire. There appears to be a regulator on the back of the alternator. I have no clue what to replace it with. I don't think it is original to the engine but it has a few years on it. Anybody have any clue on what I can use. I would also like to know how it is suppose to be wired. I have had this boat for about 5 years and there have been many things that were not right and had to be corrected. I hoping the alternator wiring is not one of them. I was thinking the wire goes to the volt meter and then to the battery somehow I just replaced the battery switch so I know it doesn't go there. The manual I have for the engine shows either a generator or alternator but both have a regulator wired it too.
 
Mot.alt.jpg

I have a .pdf file with a bunch of old MOT alternator diagrams, I am showing only one of them. Send a PM with your email if you want the file. That particular model # is not shown, but it should be of some help.
 
Brian: I'd start by calling ARCO as they are one of the front runners in the business and have a decent tech support shop. They should be able to give you options based on your current motorola number. there are only a few commonly used mounting setups and getting a compatible one (with no additional effort to mount it) is the critical part. The rest is easy, even if you have to add a wire or two.

You may also find a local electric shop that knows what makes a marine alternator. they may be able to rebuild what you have for much less than a new replacement.
 
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