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volt meter moving the wrong way-gctid404133

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    volt meter moving the wrong way-gctid404133

    I have a friend that has a 30foot 2002 Chaparral with two 5.0L MPI's Alpha drives.

    He has noticed that both volt meters on the dash of his boat will start at 13 after starting the engine and move down to 12 instead of moving up. Meaning they are not charging but discharging. This is when the both engines are running and in neutral and he will rev them up.

    The batteries are only 2 years old and he is wondering if both alternators are going out on him or if the dash volt meters have a wire crossed somewhere or something else.

    He thought he had a isolater going out and took the port side off. Could a red lead do this if not connected back the way it was before. Meaning did he put hook the isolater up wrong.


    2001 Maxum 3000 SCR
    Twin 5.0L w/ Bravo 2

    There is usually a cigarette lighter socket on the dash for 12 volt accessories. Try hooking up a digital voltmeter to this voltage source and see what happens when you rev the engines. If the DVM shows an increase in voltage (and the dash voltmeters do not) then there is some sort of problem either with the hook up or the meters themselves.
    2007 Discovery 246
    300mpi BIII
    Welcome island Lake Superior


      Battery isolators have a voltage drop of .6 to .7 volts.

      Bayliner 3870 "ALASKA33)
      Twin 350 GM power
      Located in Seward, AK
      Retired marine surveyor


        boatworkfl wrote:
        Battery isolators have a voltage drop of .6 to .7 volts.
        There are a number of possible issues.

        How long has this been going on? Is the isolator a new addition?

        What is the wiring on the alternators and how is the regulator wired?

        If the sensing wire on the alternator is on the regulator side of the isolator and not on the battery side this could cause problems.

        If the exciter wire is not direct to the battery this could result in the alternators being damaged.

        It would be helpful to have more information on the models of the alternators, type of regulators and general wiring diagram...

        Sorry to ask so many questions but we need more info to help.


          The alternators are stock from Chaparrel and that is about all I know.......

          I was hoping for the instant answer on this and I do understand all the variables that go with the question.....


          2001 Maxum 3000 SCR
          Twin 5.0L w/ Bravo 2


            Ditto Larry, and take a volt reading right at the helm power.

            Rick E. (aka RicardoMarine) Gresham, Oregon
            2850 Bounty Sedan Flybridge model
            Twin 280 HP 5.7's w/ Closed Cooling
            Volvo Penta DuoProp Drives
            Kohler 4 CZ Gen Set

            Please, no PMs. Ask your questions on forum.