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  1. Member berudd's Avatar
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    #21
    Quote Originally Posted by EuropeanAM View Post
    +1

    And if you get similar results, Alternator needs to be replaced (diode problem).
    So 30 vac is a value that's possible to see then? Would that have been caused by disconnecting the battery while it was running or hooking up the battery backwards. The motor seems to be charging the battery just fine if that matters.
    Bruce
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  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #22
    Yes, it is possible in the case of a shunted diode (or diodes).

    And yes, it could be caused by disconnecting the battery with the engine running, or a reverse-polarity connection (though the fusible link lead will most commonly burn out prior to damage).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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  3. Member berudd's Avatar
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    #23
    Quote Originally Posted by EuropeanAM View Post
    Yes, it is possible in the case of a shunted diode (or diodes).

    And yes, it could be caused by disconnecting the battery with the engine running, or a reverse-polarity connection (though the fusible link lead will most commonly burn out prior to damage).
    OK, thanks. I'll double check and report back.
    Bruce
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  4. Member berudd's Avatar
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    #24
    I checked it today with the different meter and got somewhere between 25 and 30 V AC. So does this mean I need a new alternator or is there some other part I can replace it instead?
    Bruce
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  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #25
    If you got high voltage at the large RED output terminal with the engine running- you have a BLOWN FUSIBLE LINK LEAD.

    Replace the fusible link lead (be SURE to disconnect battery power FIRST).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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  6. Member berudd's Avatar
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    #26
    Quote Originally Posted by EuropeanAM View Post
    If you got high voltage at the large RED output terminal with the engine running- you have a BLOWN FUSIBLE LINK LEAD.

    Replace the fusible link lead (be SURE to disconnect battery power FIRST).
    That was blown and I replaced it. The 30vac reading is accross the battery while idling.
    Bruce
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  7. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #27
    A reading above 0.25 VAC at the battery terminals is an indication that the alternator needs to be replaced.

    Make sure your meter's AUTO-RANGE feature is turned OFF.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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  8. Member berudd's Avatar
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    #28
    Thanks Don. I checked it with two different meters. Neither had a auto range.
    Bruce
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  9. Member
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    #29
    Sounds like an your alternator is toast
    Former USAF Gunner B-52H

  10. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #30
    Definitely does sound that way (diode failure more than likely).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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