SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: Hawaiian22 on August 07, 2021, 12:50:24 PM

Title: Replacement for Mototola mr12n451d alternator
Post by: Hawaiian22 on August 07, 2021, 12:50:24 PM
Hi,

Been a while since I've posted..Hopefully someone can help me out.

I have a mid 70's Ford 460. The alternator has failed on it. It is a Mototola mr12n451d.
I'm  looking to replace it with something compatible and more readily available but can't find any details that really help me cross reference it. A replacement Mototola mr12n451d is a bit expensive, and I'm seeing 100amp + alternators around $100 or less.

Any help would be really appreciated.
Thanks

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Title: Re: Replacement for Mototola mr12n451d alternator
Post by: mash on it on August 08, 2021, 12:27:31 PM
Exposed engine? Just a run of the mill GM 1 wire or even a 3 wire alternator.

Covered engine- a GM marine unit, pretty easy to source, ebay, Amazon, CP performance, jegs or summit.

Your brackets may need some adjustments, should be fairly easy.

Dan'l
Title: Re: Replacement for Mototola mr12n451d alternator
Post by: Hawaiian22 on August 08, 2021, 04:38:32 PM
Exposed engine? Just a run of the mill GM 1 wire or even a 3 wire alternator.

Covered engine- a GM marine unit, pretty easy to source, ebay, Amazon, CP performance, jegs or summit.

Your brackets may need some adjustments, should be fairly easy.

Dan'l
Thanks for your reply. The boat has a covered engine... so I'll  definitely be buying a marine alternator.

The Motorola has one wire(battery), and a second wire yellow.. i believe is an exciter wire coming off of the voltage regulator.. without cutting the wire loom apart the second wire either goes to the coil, or the fuse block.

How would i wire that second wire, if it is an exciter wire to an internal voltage regulator single wire design alternator?

That is really all that is stumping me, as I'm not very knowledgeable with automotive electrical systems.

Thanks,
Kory



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Title: Re: Replacement for Mototola mr12n451d alternator
Post by: Rogers57x on August 09, 2021, 03:08:59 PM
Had the same problem,  tried the 1 wire gm only to find out it would not fit my plate system without grinding  the plate down because the alternator  was much fatter around with all the headaches of that and rewiring  I just took it to a alternator repair  shop and for  $150 he rebuilt it,  problem solved hope this helps
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