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3870 Wiring Basics

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    3870 Wiring Basics

    I have a couple fairly simple wiring projects that I need to start on. I need to run new constant power to my aft bilge pump so the float switch works again. Presently the pump works from the switch at the helm but the power to the float switch is all green and corroded and even though I can sense power on it, the wire is too degraded to use. I will also have to run some power out to where I want to mount electric downriggers on my transom (gunwhales?)
    The simplest way to do this would be to run fused red wires straight from the battery but I don't really want to do it that way. I would rather take power off one of my existing breaker panels. I'm just wondering what the best place to take power from would be. I have available breakers on my main panel, panel1, and panel2. Then again, I'm planning on running a two-trap line puller from one of the downrigger positions and I'm a little concerned about line loss if the run gets too long. Any suggestions? Also could use advice on the best way to pull the power out to the downriggers. Are you able to mount the female receptacles right in the transom?

    #2
    I had both of those situations. I added two twist in type fuse holders to the battery switch panel inside the engine room door. 14ga should be plenty good for the bilge pump, but I see 10ga for the downriggers. As it turns out, I had run new 10ga for the diesel furnace forward to the engine room bulkhead then across to the starboard side and aft that turned out to be beyond salvage, so I repurposed the wires for the downriggers. By the time the wires get to the plug on the port side, they’ve gone farther than need be, so, when I install the new diesel furnace I’ll be rerouting those wires.
    Several years ago the ABYC changed the 12v negative wire to yellow. It makes it a lot less confusing when there are 120v wires nearby.
    P/C Pete
    Edmonds Yacht Club (Commodore 1993)
    1988 3818 "GLAUBEN”
    Hino EH700 175 Onan MDKD Genset
    1980 Encounter Sunbridge "Misty Blue" (Sold)
    MMSI 367770440
    1972 Chevrolet Nova Frame off Resto-mod in the garage
    Boating on the Salish Sea since 1948

    Comment


      #3
      I never use 14 ga on a bilge pump, min. 12 ga, and that can depend on the size of the pump, I have 3 in my aft bilge, largest I run 10 GA.
      All the original wiring on my 3870 has been replaced including battery cables which are 2/0.
      All the neg wires except the 2/0 battery cable are yellow, could not get a good deal on yellow positive battery cable.
      Pat says: DO-IT-RIGHT THE FIRST TIME!

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

      Comment


        #4
        Boatwork, I knew someone would chime in with a better wire size recommendation. I was waffling between 12 & 14 and chose the smaller because the run is short and I assumed a fairly small draw pump. Bigger. Is better.
        P/C Pete
        Edmonds Yacht Club (Commodore 1993)
        1988 3818 "GLAUBEN”
        Hino EH700 175 Onan MDKD Genset
        1980 Encounter Sunbridge "Misty Blue" (Sold)
        MMSI 367770440
        1972 Chevrolet Nova Frame off Resto-mod in the garage
        Boating on the Salish Sea since 1948

        Comment


          #5
          Thanks guys. I bought forty feet of 10ga marine wire so I'll just use that for both. I was wondering why the neutral wire was yellow, that does make sense to distinguish it from AC. How did you install your downrigger receptacles Pete?

          Comment


            #6
            I ran 10 ga around the back from the port side on my 3870 2 down riggers, I have access holes on the back corners covered with dark plexi glass to run the wire.
            Pat says: DO-IT-RIGHT THE FIRST TIME!

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

            Comment


              #7
              Bry, you are going to love it. The mounts are above the teak and can be removed easily. I even have one for my bbq.
              P/C Pete
              Edmonds Yacht Club (Commodore 1993)
              1988 3818 "GLAUBEN”
              Hino EH700 175 Onan MDKD Genset
              1980 Encounter Sunbridge "Misty Blue" (Sold)
              MMSI 367770440
              1972 Chevrolet Nova Frame off Resto-mod in the garage
              Boating on the Salish Sea since 1948

              Comment


                #8
                I was wondering why the neutral wire was yellow, that does make sense to distinguish it from AC.
                Please correct if I am incorrect but IIRC DC wiring is red= power, (positive), yellow= Negative. There is no neutral in DC wiring. AC wiring is black= power, white= neutral and Green= ground.
                Jim Gandee
                1989 3888
                Hino 175's
                Fire Escape
                Fyrflyer@ca.rr.com

                Comment


                  #9
                  You ay want to keep the negative 12 volt DC wire on the boat black if your current system has black neg. 12 volt wire.
                  possible exception would be if you use a red/yellow jacketed pair cable.
                  Last edited by boatworkfl; 03-03-2018, 12:25 PM. Reason: sp
                  Pat says: DO-IT-RIGHT THE FIRST TIME!

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

                  Comment


                    #10
                    You are correct Jim, I should have said negative instead of neutral. The wire I bought is the jacketed red/yellow pair so I'll just use that. That is a nice system Pete, I can see I'm going to have to put a little motre thought into how I want to mount my downriggers. I thought it would be as simple as screwing them into the teak and gunnels but I can see that is not going to work. The Scotty base plate that I wanted to use is already wider than the teak cap on the gunnel so I'm going to have to do something else. If the weather holds up I may head out today to try a little jigging though, don't need downriggers for that.

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