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Gas tank sending unit wiring diagram help

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  • Gas tank sending unit wiring diagram help

    Does anybody know how the wiring is hooked up to a gas tank sending unit? I've seen the boat wiring diagram, but that is showing the gauge end. My sending unit on the tank has 2 connectors, not including the mounting screws to the top of the tank. I'm either not getting +12v through the circuit, and the tank, being aluminum, would itself provide the grounding and the other connector would be the signal wire to the gauge, or the sending unit is bad. But it would be helpful if I knew for sure which way the wiring is on the sending unit.

  • #2
    Re: Gas tank sending unit wiring diagram help

    I looked at a wiring diagram for a version of my boat that had a permanent gas tank( mine does not) and it has a black and a pink wire running to the sender.

    you have to have ground get to the tank...you cant assume the tank is grounded by its mounts.

    for sure the sender usually is a pink wire..

    it seems lots of boat have non working gas gauges

    good luck



    • #3
      Re: Gas tank sending unit wiring diagram help

      The sending unit should have two wires coming out of it. They are non polarity sensitive. This means you can hook them up any old way and they will work.

      The sender wires should go through the harness connector behind the dash ending up at the gauge. At the gauge one of the two wires usually pink will be connected to the "S" Terminal on the fuel gauge and the other wire (usually black) connects to all the other black wires on the GND Terminal on the back of the gauge.

      If your having problems run a separate two conductor wire directly across the deck from the gauge to the sender to test the sender minus the boat wiring.


      • #4
        Re: Gas tank sending unit wiring diagram help

        There is a pin in the center of the sender, that goes to the guage. The sender works on resistence, but that is not important unless your gauge is not working.The other wire is a ground wire. If you are not sure you have a good ground, hook up a ground straight from the battery to the tank ground and then to the sender ground.


        • #5
          Re: Gas tank sending unit wiring diagram help

          1. with key on, bridge or connect center wire on tank (usually pink) to the tank ground wire. If the tank has a spade connector, make sure its clean and tight.

          a. if Gage pegs to full, problem is in the sender in the tank (most likely)

          b. if gage does not move, ground the tank to the negative battery terminal and see if the gage pegs. If gage reads, problem is in the tank external ground.

          C. if none of these test work, go to the back of the gage and check connections, S to G should cause gage to peg, if it doesn't, see if the gage is getting power at the ign terminal. if the gage is getting power and jumping sender to ground on the gage does not cause gage to peg, you have a bad gage.

          All this checking and poking around the tank, inspect to make sure there are no gas leaks or smell of gas in any way shape or form, Any leak could be a death sentence and need your immediate attention.

          Good luck
          Farmer's Tan....year round


          • #6
            Re: Gas tank sending unit wiring diagram help

            forgot to mention,

            I have seen some older boats that have sticky floats.

            On one boat I made a fist and hit the tank next to the sender and "fixed it fonzy style"

            On another I used the but end of a craftsman screw driver, Yes a craftsman. Back in the day Crappy man made a good tool, they are still guaranteed.
            Farmer's Tan....year round


            • #7
              Re: Gas tank sending unit wiring diagram help

              Ok, thanks for replys, that will definitely help me. Some Jack leg idiot has got what looks like an extension cord of a fairly large gauge, like maybe 12 gauge wire, hooked up to it, and had wired a jumper to the battery from the center terminal. So they were possibly attempting to bypass the control box ignition key. Which might mean I have no +12v power out to the back of the gauge on the dash. Think I'll fish a new set of wires for this that are color correct while I'm at it.


              • #8
                Re: Gas tank sending unit wiring diagram help

                Here you are:


                • #9
                  Re: Gas tank sending unit wiring diagram help

                  Nice work Silver

                  I could use that one to help a bunch of peeps at work.
                  Farmer's Tan....year round


                  • #10
                    Sign up today
                    Re: Gas tank sending unit wiring diagram help

                    Silvertip and all of you with the good info, Thanks a heap. I'm looking at this HydraSport, as a candidate for more than just this fuel gauge rewire. I stuck my head down under the dash and along the underside of the gunnal, and was shocked and afraid at the same time. It looks like a explosion of wire going on. It looks a mess under there. I should have guessed it would be like that when I saw the extension cord wire for the fuel gauge. And no fuses anywhere, YIKES!