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  1. #1
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    Optimax 250 ProXS not charging battery

    My brother has a 2012 Optimax 250ProXS out of warranty that is giving an engine alarm and showing low voltage. Took it to the dealer and they charged $300 and said it was the battery. We have replaced the battery with a new battery but it is still doing the same thing. Contacted the dealer and they said to bring it back in and they will look at it again. Another $300 I pressume. We noticed that when the motor is running the voltage on the smart craft guage is going down instead of up, which makes us think it is running off the battery and not getting a charge from the alternator. Voltage at the beginning of the day starts around 12.7 volts and continually drops all day until it gets around 11volts then the alarm comes on. The more or faster you run, the quicker the voltage drops. I have a 2014 Optimax and when my motor is running the battery voltage jumps from 12.7V up to 13.6 volts. We have eliminated the battery as the problem and think the issue is either the alternator or wiring/fuse between alternator and battery. Saw a posting on another forum about similar issue where problem was determined to be a "fuseable link between the alternator and battery". Anyone know where this fuse would be and what size it should be. We are not mechanics but we can replace a fuse if we can find. Thanks!!!

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    #2
    Fusible link is built in to the red wire from the alternator to the main power lug on the motor. Check it for continuity with a multimeter. Also if it’s blown and you crank it the motor and check the alternator output to ground it will read 20+v instead of the 14 it reads under a load.

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    #3
    So does that mean it is not a fuse which I can replace myself?

  4. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #4
    Quote Originally Posted by mrc View Post
    So does that mean it is not a fuse which I can replace myself?
    You replace the whole wire which contains the fusible link.
    If you have integrity, nothing else matters. If you don't have integrity,
    nothing else matters.​

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    #5
    It’s made into the harness. Typically replace the whole harness fairly expensive for what it is.

    I suppose you could replace just the fuse section but I would be sure to replace it with an identical fuse (slow vs fast blow, etc). It’s there to protect your alternator and it’s most definitely cheaper than an alternator so I would go ahead and replace the harness with the correct OEM part.
    Last edited by Jtreed99; 03-21-2018 at 12:36 PM.

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    #6
    Thanks all. Will update the thread in a few days with results of replacing the link wire.

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    #7
    As easy as it is to test I would surely test it and the alternator before just replacing it. I think mine was like 70-80 bucks.

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    #8
    I tested it. No continuity between alternator and positive on battery. No voltage between alternator and engine ground. Got to be the fusible link wire. Let you know in a few days. Thanks!!!

  9. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #9
    Quote Originally Posted by mrc View Post
    I tested it. No continuity between alternator and positive on battery. No voltage between alternator and engine ground. Got to be the fusible link wire. Let you know in a few days. Thanks!!!

    First sentence says the fusible link link lead is blown.

    Second sentence says there’s an error OR there is another problem.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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    #10
    Hopefully he meant he checked that voltage without the motor running and doesn’t need an alternator as well...

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    #11
    Two problems.....the fusible link issue happened when the battery was changed and the wrong connections where made, creating problem #2. Still have to find #1 problem.



  12. Member
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    #12
    Problem solved. Replaced the fusible link. Now get continuity on the link and 12V with the motor off between the alternator post and engine ground. $80 for the wire and 30min to replace. Thanks for the info on the fusible link. You guys are great!!!

  13. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #13


    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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