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  1. #1
    Petty Officer 3rd Class UNSUREBOATGUY's Avatar
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    Default New Alternator-Wiring Question

    1987 Mercruiser 3.0 Alpha 1

    Just picked up a new alternator for the boat. Its a Sierra 18-5951 3 wire alternator. My question has to do with how to wire it up to the engine. The Orange and black wires are self explainatory, but which wires do I hook up to the red/purple and purple wires coming from the engine harness? The alternator has a black wire and a red wire.

    Do I assume that the red wire is colored correctly and that the black wire on the new alternator would have been white on the original? (I never saw the original-I'm replacing an automotive alternator, and I have my doubts whether it was hooked up properly.)

    I looked at the manual, but it is still unclear to me. Maybe I just looked in the wrong spot. I looked at section 4C in Manual #10.

    Thanks a bunch!

  2. #2
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: New Alternator-Wiring Question

    You aren't going to find it in the manual, because Mercruiser never used that type alternator.

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    Don S.


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  3. #3
    Petty Officer 3rd Class UNSUREBOATGUY's Avatar
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    Default Re: New Alternator-Wiring Question

    Thank you very much.

  4. #4

    Default Re: New Alternator-Wiring Question

    Im having the same problem. So does the purple and red go to the red and the purple to the black??

  5. #5
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: New Alternator-Wiring Question

    Quote Originally Posted by Gamecock1 View Post
    Im having the same problem.
    Then you need to start your own thread, with your engine information, and your question.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  6. #6

    Default Re: New Alternator-Wiring Question

    Same engine, same alternator, same year, same question. I wasnt aware i needed to start a new thread sorry. It looks to me the red and purple coming from the engin harness goes to the red wire and the purple wire goes to the black wire. Just was looking for some confirmation.

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