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  1. #1

    Default Testing Alternator

    How do you test your altinator? I had a dead battery today and the battery needed replacement. However, I am also worried that the altinator may be bad (just parinoid) and wanted to test it before going out again? I have an outboard: 2004 Mercury XR6 150.

  2. #2
    Petty Officer 3rd Class koko1's Avatar
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    Default Re: Testing Alternator

    Any auto parts store should be able to test it for you free of charge.

  3. #3
    Moderator achris's Avatar
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    Default Re: Testing Alternator

    The alternator can be tested by putting a multimeter on the battery. Check it with the engine running at about 1000rpm... Should be around 14.5 volts on a fully charged battery.

    Auto shops can't check it... Probably wouldn't know where to start...

    Chris.......
    The world takes on a whole new perspective when viewed from 100' below...



    1972 Bertram 'Bahia Mar' 20
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  4. #4
    Petty Officer 3rd Class koko1's Avatar
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    Default Re: Testing Alternator

    Quote Originally Posted by achris View Post
    The alternator can be tested by putting a multimeter on the battery. Check it with the engine running at about 1000rpm... Should be around 14.5 volts on a fully charged battery.

    Auto shops can't check it... Probably wouldn't know where to start...

    Chris.......

    Guess it depends on where one lives... Around here they check everything from batteries to alternators to starters

  5. #5
    Moderator achris's Avatar
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    Default Re: Testing Alternator

    Quote Originally Posted by koko1 View Post
    Guess it depends on where one lives... Around here they check everything from batteries to alternators to starters
    The outboard alternator is so unlike a car alternator that the average auto shop wouldn't even know where to start looking for it.

    It consists of the stator windings under the flywheel, the flywheel and the rectifier.... Not the sort of things you can just unbolt and take in...

    Chris........
    The world takes on a whole new perspective when viewed from 100' below...



    1972 Bertram 'Bahia Mar' 20
    2006 Mercruiser 4.3MPI (0W617679) w/Alpha 1 Gen II (0W829301)
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    Please don't send service questions in private messages. That's what the forum is for. Messages of thanks, always accepted.
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  6. #6
    Admiral j_martin's Avatar
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    Default Re: Testing Alternator

    Quote Originally Posted by koko1 View Post
    Any auto parts store should be able to test it for you free of charge.
    If you can't identify one in a well lit room, please don't offer advise.

  7. #7
    Supreme Mariner Silvertip's Avatar
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    Default Re: Testing Alternator

    If the console of your boat has a gauge with VOLTS on the face, start the engine, rev to 1500 rpm and look at the gauge. You have a 12 volt battery so if the meter reads anything more than 12.6 (typically 13 to 14.5 volts) the alternator is working; Because the alternator is working, that does not mean you have a battery capable of accepting or holding a charge. Any auto store can load test it for you. If your boat doesn't have a voltmeter, a 10 buck hand held multi-tester (volt/ohm meter) will work. Just set it to read 12 volts (20 volt scale) and connect it to the battery.

  8. #8
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    Default Re: Testing Alternator

    Quote Originally Posted by koko1 View Post
    Any auto parts store should be able to test it for you free of charge.
    Probably true, except most in the US don't have facilities for starting and running outboard engines in their parking lots. They'd only be able to do the simple output tests that you can do yourself. Trouble shooting and replacement would need to be done at a Marine facility.

    Now if it was an Opti-Max with a mini-automotive alternator then yes, you could take it off and most any automotive stores should be able to test it. Most of those were made by Delco but I think Nipondenso makes them now.

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