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Voltage Gauge and Rough Idle

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  • Voltage Gauge and Rough Idle

    Hi Everyone,

    This last weekend was the first time in 2 seasons we had our boat out. Battery was replaced 2 seasons ago and charged as needed. For the life of me I cannot remember where the voltage gauge should be reading when in accessory and where it should be when it’s running at idle or under load. My readings from this weekend are below.

    key on: Gauge reads 11v
    running at idle (cold): Gauge reads 11-12v and had slight rough idle
    under load: Gauge reads 13v
    running at idle (warm): Gauge reads 13v
    key on after being off for 20 minutes: Gauge reads 11-12v
    running at idle after being off for 20 min.: Gauge reads 11-12v then back to 13v after warm.

    I also noticed that going from wot or close to it, down to a lower RPM or neutral, the voltage gauge would bounce down to that 11-12 lv and then back to 13v.

    Fuel with stabilizer is 2 years old as well so that could be part of the idle

    Is it time for a new battery again or could it be the Alternator? Or is it all in my head?

    2003 Bayliner, Merc 3.0, Alpha I Drive

    Let me know your thoughts and you you!





  • #2
    Many of the boat gauges are not very good except when they where new.

    Measure the voltage when running at the battery. If you get 14+V when motor is running your good there. Check also at the Red/Purple wire at the key switch. If all good then its the gauge and/or its connections
    94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
    95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
    07 Seadoo GTX
    Merc Adults Only VP Adults Only
    G-Dad always said "First Liar doesn't stand a chance"

    Comment


    • #3
      Tested it today and with motor off, Battery reads 16.5v and when running 19.8v. Guessing it is a bad gauge. Idle problem went away too. Must have been cold old bugger that day. Let me know if the battery test sounds right. Thanks again!

      Comment


      • #4
        Sign up today
        Motor OFF and 16.5V yes that is a bad gauge
        94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
        95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
        07 Seadoo GTX
        Merc Adults Only VP Adults Only
        G-Dad always said "First Liar doesn't stand a chance"

        Comment

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