Trolling Motor Regulator

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Joined Jul 25, 2008
I have a large boat and am planning on hooking multiple trolling motors down the side. I can't afford to buy multiple new ones so their thrust matches. Instead, I will be buying cheap used ones. With them being used and in various conditions, I can't guarantee their thrust even if they are rated the same (assuming it was even accurate when new). So I am planning on ripping out the speed control from the motors. On the one I have so far, it appears that the motor has multiple coils (wiring paths) so that you power these two wires for full power, these two for half, etc. I want to just use the full-power wires and wire in a variable switching regulator to lower the speed. No single motor will be large enough to require a 24v source, but if the regulator requires it to get up to a full 12v (ie, its output will be a max of input minus 1.2 or something) then I can push up to 24, although I won't until I get all motors working with the 12 (and just won't have true full power yet).

The switch I have pictured in my head would be some sort of rotary double-throw switch, such that when set in the middle, the motor at the front and back both have full power, when set to the left the front motor has full power and the back one none, and when set to the right the back motor has full power and the front one none. (It is probably more realistic for the middle position to have both motors at half power, but I would prefer full.) I will use this to fine-tune the boat position relative to the shore and wind. I will also have a polarity switch further down the line so that I can drive the back motor in the reverse direction if needed.

I don't know what a typical trolling motor will draw, but the circuits are normally fused for 15 or 20 amps, so the regulator will have to handle that. Also, the control wire may have to run 30ft or more from the power wires (27ft boat). Also, I eventually plan to go all the way up to 4 trolling motors. I only need to match the front half to the back half, so I won't need to match the two back ones to each other, but this may require the voltage regulator to have to handle 40 amps. I'm fine (and it would probably be cheaper) if it is two separate regulators on the back two motors as long as they can both be controlled with the same switch/control wire.

I've built linear regulators before, but can't afford the wasted power. By the time I am through, I am hoping to have enough combined thrust that if I have to run them at full power (other than chasing a school of fish), it is probably too windy for me to be out in the first place.

Oh, and in case it isn't obvious, my main concern is that it be as cheap and simple as possible. I went through a lot of trouble using over-powered capacitors and such for my last linear, because I was powering laptops and didn't want to risk any ripple. I'm assuming things like this won't be necessary for trolling motors.
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