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Trolling Motor Current Draw ??

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  • Trolling Motor Current Draw ??

    I'm ripping most of the wiring out of the boat I just bought and starting over from scratch, way too much "redneck engineering" for my taste. Anyway, what kind of current draw should I see from a 45 pound thrust trolling motor (12 V)?

    thanks
    1979 Checkmate Eluder
    rebuild thread - http://forums.iboats.com/showthread.php?t=541058
    1990 Johnson GT-200 (Died) - http://forums.iboats.com/showthread.php?t=537238
    1993 Rude 175


  • #2
    Re: Trolling Motor Current Draw ??

    Don't know for sure about a 45 but a 55 draws 42 amp at full speed. That might get you in the ball park.
    "A manual is a cheap investment"
    Fair Winds and Following Seas
    Bill
    PTC USN ret

    Comment



    • #3
      Re: Trolling Motor Current Draw ??

      Thanks. Me thinks the 12 guage wire the previous owner had installed (complete with 5 butt splices) is a bit lacking.
      1979 Checkmate Eluder
      rebuild thread - http://forums.iboats.com/showthread.php?t=541058
      1990 Johnson GT-200 (Died) - http://forums.iboats.com/showthread.php?t=537238
      1993 Rude 175

      Comment



      • #4
        Re: Trolling Motor Current Draw ??

        I have a Motorguide 68lb Brute 12/24 and it has 40 amp fuses in line with each battery on 6 AWG wire, 17' boat. So, speculating, if I run on half the voltage the thrust will only be half so looks like this motor would deliver 34 lbs of thrust at a comfortable current below 40 amps on the 12v switch position.

        Gonna say you can do it on 40 amps, but fuse higher otherwise you may be blowing fuses on long full speed runs. 6 AWG is kinda light for 40 amps, but since wires aren't usually bundled together tightly allowing the wire to run cooler, and with a good thermoplastic 105F coating on the hookup you should be good to go. 4 would do better, but in a boat you have to do a little compromising due to weight. Also, if you aren't hammering down on it at full throttle for extended periods of time....constantly, you won't have a problem.

        Mark
        If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

        Comment



        • #5
          Re: Trolling Motor Current Draw ??

          6 gauge wire is standard rigging for trollers up to 55# at 12V on the average boat. I routinely run my 55 on its fastest speed to move between holes in skinny water and the wires don't begin to get warm. 8 gauge will be ok in your application as well.

          Comment



          • #6
            Re: Trolling Motor Current Draw ??

            As we speak I am testing my Endura 30 in the garage. I got 10-12 amp draw before I burned out my 10 amp voltmeter. Minn Kota manual says says figure 30 amps
            (approx 1:1 ratio) for a 12v motor so I do not know if it pulls more power in the water. For design assume 1:1 on 12-volt, I believe is good.

            I would like to draw less amps. Does anyone know what the lowest amp draw 24v troll motor is? I was thinking one of the new Minn Kota with digital speed reduction at low speed, but I hate to pay $500 just to measure it.

            Comment



            • #7
              Re: Trolling Motor Current Draw ??

              Any electric motor free running draws far less current than it does with a load (as in the water). It draws the highest amount of current with a stalled rotor. To get less current draw, you need a motor with less thrust. Less thrust means you are less efficient pushing (or pulling) the boat. There is no free lunch here. When it comes to trolling motors, pick a motor that will do the job. Then to power it, buy the largest capacity deep cycle battery you have room for. Maximizer circuitry is effective at lower speed settings. At maximum speed settings it doesn't matter much which technology you have.

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              • #8
                Re: Trolling Motor Current Draw ??

                Silver- I am playing around with my canoe. So I would like to know the lowest possible amp draw motor I could get at low speed - assuming this would be a 24-volt. Something like a MotorGuide 24v Brute Competition @ 54-lbs thrust with Dura max variable speed should be pretty low amp draw at the slowest setting? Does not seem like this motor is made anymore but I saw it on Craigs list.

                As far as the original poster, the person can get detailed wire size instructions from the Minn Kota site FAQ.

                Comment



                • #9
                  Re: Trolling Motor Current Draw ??

                  You are going to lug around two batteries in a canoe? A 25#, 12V motor is more than enough to push a canoe. What's the big deal about current draw? Buy a 40 - 45# Minnkota power drive with maximizer and run it on low speed. You need only one battery and it will likely run for two days or more on a charge (depending on battery capacity). Old trolling motors (non-maximizers) used speed coils to control motor speed. These were nothing more than wire wound resistors that bypassed the motor and shed the heat through the water. They used nearly as much current at the lowest speed as they did wide open. In a nutshell, the most efficient use of power is achieved with the current Minnkota or MotorGuide motors with the maximizer (Minnkota term) or digital technology.

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                  • #10
                    Re: Trolling Motor Current Draw ??

                    Silvertip- Well I was going to "lug" 2 really small batteries to get 24v. But I need a really low power motor, maybe would have to be an unconventional motor. Or maybe I could put another PWM on a MK with digital maximizer and pulse it. Can you buy an external PWM for something like an Endura that does not already have PWM?

                    Comment



                    • #11
                      Re: Trolling Motor Current Draw ??

                      I run a 30lb Motorguide on our 17' alum lake canoes. On the top two settings you have to set the motor very deep to prevent cavitation behind the shaft getting to the prop. We normally run on settings 2 or 3. Our old Herters elec motor which was around 15-17lb thrust was plenty for the canoe.

                      Can you post some more info on why the low current draw is your driving requirement? Buying and using a large 24v speed controlled elec motor at its slowest speeds and dealing with dual batteries, on a canoe, seems like an extreme waste and a big pain to deal with. Small and light, and easily removable, are usually key canoe requirements.

                      Comment



                      • #12
                        Re: Trolling Motor Current Draw ??

                        I'm really confused on the overall logic. Two "really small" batteries (such as??) will likely have less capacity than one standard deep cycle. Using virtually any 12V troller (pulsed or not) will drive that canoe just fine for a great distance. As with a gas engine, it takes so much fuel to make so much HP. With an electric motor it takes a given amount of current to produce a certain amount of thrust. Yes -- there are certain technologies (we mentioned them) that can help prolong battery life at slow speed. But at their maximum thrust, both pulsed and standard motors will draw about the same current. Your choice is to go new technology or build your own pulse unit for an old motor - but don't be surprised if the efficiency is still worse than the newer motor.

                        Comment



                        • #13
                          Re: Trolling Motor Current Draw ??

                          I am trying to run motor off a 64 watt solar panel, that puts out 4 amps on ebay for $280. My Endura 30 takes 10-amps, no matter what speed, on the bench, though only 8 amps in reverse. Maybe a newer Digital Maximizer PWM motor would take less current at the lower speed. I bought some smaller solar panels, but too small I guess unfort. Canoe moves pretty good at low power settings.

                          Comment



                          • #14
                            Re: Trolling Motor Current Draw ??

                            This entire thread would likely have been much shorter had you mentioned this "detail" a little earlier. Four amps will not get it done. I hope you aren't back in the wilderness on a cloudy day and have to get out in a hurry. Isn't a 64W solar panel a little large to hang on a canoe, and subject to wind gusts? Sounds like a good idea but whether or not it's practical is questionable.

                            Comment



                            • #15
                              Re: Trolling Motor Current Draw ??

                              Sorry. But anyway at 29x54-inch the 4-amp panel should fit inside a 17-ft Grumman on the floor. Yes could indeed be a very good sail, especially the flexible panels. I think you might have something there. Thank you for the responding. OK time out for xmas.

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