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Thread: Hotwire an old electric trolling motor?

  1. #1
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    Default Hotwire an old electric trolling motor?

    I have an older MinnKota Turbo 65 trolling motor with a fried speed switch, and apparently Minn Kota no longer makes replacement switches for this model. So, the first question is whether some reader out there has worked on MinnKota motors and knows which part number switch I can substitute? (my Serial # MKO 1731170, switch number 206-4020) I am hoping to make this motor usable rather than throw it in a landfill. So far, the company is no help by phone, email, or chat. I can do an end-run around the "speed coils" and the thing seems to turn full speed, (and all the speed coils seem to have continuity.) If my creaky memory serves, the company used to manufacture an electronic module for speed control, (Maximizer?) but it was apparently discontinued. I note that the battle-bot robot supply companies sell solid-state controllers that claim to provide forward / reverse motor control at high current with various inputs, (I think I can understand the analog inputs, definitely not the digital ones) Unfortunately many of these suppliers are using dubious English translators. Can anyone help me either with a spec for a switch or a PWM solution? Please help keep this motor out of the garbage dump!

    fwiw, I fried the switch while experimenting with different propellers to get closer to hull-speed in a 1920 era Rangeley Lake Boat, 17', The Prop was an 11x7 scimitar shaped model-airplane prop with the motor running in reverse.

    Thanks,

    Ken

  2. #2
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    Default Re: Hotwire an old electric trolling motor?

    I'd think that any local auto electrics specialist will sort something here....its a switch after all, not windings. not commutators or brushes,...they will suss the problema quickly and if it does turn out to be more 'internal' they will probably have a solution too. You might have to cobble up some sort of nacelle or swith cover if tey sort it but leave you with a switch more open to the elements, but it won't be difficult.
    'C'est la vie' say the old folks it goes to show you never can tell

  3. #3
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    Default Re: Hotwire an old electric trolling motor?

    I did the same thing last week with my 80 lb. thrust MinnKota. Fried the reverse part of the switch with a RC plane prop on it when I hit some weeds.
    I can get a replacement switch/controller, but the original is really glued in there. Plus, the stupid thing cost $150!
    I was born on a wooden boat that I built myself.

  4. #4
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    Default Re: Hotwire an old electric trolling motor?

    Google a potentiometer suitable for DC and that is rated for the max amps of the motor. Ex" 48 volt dc potentiometer."


    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  5. #5
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    Default Re: Hotwire an old electric trolling motor?

    Quote Originally Posted by Breakaway View Post
    Google a potentiometer suitable for DC and that is rated for the max amps of the motor. Ex" 48 volt dc potentiometer."


    Kevin
    Not practical: I started my adult life in theatre lighting at a time when we still occasionally had to deal with resistance-type potentiometers for lighting control. (early-60's) One such unit capable of 15 amps weighed about 20# and was the size of a large serving platter. The 80# motor mentioned by the previous post draws about 55 amps and the potentiometer would be gigantic. Besides this, all the extra energy goes into heat rather than into moving the boat. PWM stands for pulse width modulation and it amounts to turning the juice on and off very rapidly while varying the proportion of on vs off time. The waste while the juice goes from on to off is much less, but still not inconsequential, so it is much better as long as the engineers filter out the Radio Frequency trash that results from all those voltage spikes.

    Ken

  6. #6
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    Default Re: Hotwire an old electric trolling motor?

    I should have added that the "speed coils" on an older trolling motor appear to be nothing more than a potentiometer with 3-5 steps rather than being continuously variable. They were smaller because they send the wasted energy into the water which is very efficient at conducting heat. It could have been more efficient (and expensive) if they had varied the field current to change the speed, (inversely proportional) but now that there are solid-state options, this would seem to be the way to go, I just don't know how to spec / order / and set such a thing up.

    Ken

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    Default Re: Hotwire an old electric trolling motor?

    There is nothing quite as permanent as a good temporary repair.

  8. #8
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    Default Re: Hotwire an old electric trolling motor?

    Amazon sells all sizes of dc controllers for surprisingly low prices. I put one on an old 40# trolling motor. With a polarity reversing switch down stream it makes a easily used control. Get something in the 500-600 watt range so you aren't running it at max capability.
    If you don't know where you're going, you might not end up there.-Yogi Berra

  9. #9
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    Default Re: Hotwire an old electric trolling motor?

    Like this?
    DC Motor Speed Controller, Motor Driver Speed Control Board for Brush Motor 9V-60V 20A 1200W High Power PWM Controller DC 12V 24V 36V 48V 60V Regulator Dimmer Governor Pulse Width Modulator
    Price: $12.60
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  10. #10
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    Default Re: Hotwire an old electric trolling motor?

    Quote Originally Posted by MN Dave View Post
    Like this?
    DC Motor Speed Controller, Motor Driver Speed Control Board for Brush Motor 9V-60V 20A 1200W High Power PWM Controller DC 12V 24V 36V 48V 60V Regulator Dimmer Governor Pulse Width Modulator
    Price: $12.60
    Exactly. Running at high loads continuously you want plenty of air flow over the heat sinks. DAMHIK.
    If you don't know where you're going, you might not end up there.-Yogi Berra

  11. #11
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    Default Re: Hotwire an old electric trolling motor?

    Quote Originally Posted by Ron Carter View Post
    Exactly. Running at high loads continuously you want plenty of air flow over the heat sinks. DAMHIK.
    Sounds good. Some waterproofing might be needed? I looked at it again and then the video from the other trolling motor post https://www.youtube.com/watch?v=I5xTHJBuV1Q The wires on the 80 lb Minn Kota are much bigger. So I'm wondering if the link to the Drok controller was not so good. The reviews indicate poor workmanship, low continuous duty and things getting hot. So maybe a step in the right direction but something a little more robust is needed?
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  12. #12
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    Default Re: Hotwire an old electric trolling motor?

    Hi...i would suggest to supply B+ to the ignition coil. Use a remote starter button clipped between positive and the start terminal on the starter.
    Disconnect B+ to the coil when you want to shut it down.

    printed circuit assembly
    Last edited by TimiSchor; 01-04-2019 at 12:51 PM.

  13. #13
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    Default Re: Hotwire an old electric trolling motor?

    ???
    If you don't know where you're going, you might not end up there.-Yogi Berra

  14. #14
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    Default Re: Hotwire an old electric trolling motor?

    Quote Originally Posted by Ron Carter View Post
    ???
    They do electric a little different down in Texas

    You might also look into how they used to control fans back in the twenties. And railroad locomotives. They used different resistors to vary the voltage. You get speed jumps that way but it worked fine and was pretty simple.

  15. #15
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    Default Re: Hotwire an old electric trolling motor?

    Lots of stuff on YouTube, so **some of it** might be useful -
    https://www.youtube.com/results?sear...trolling+motor
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

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    Default Re: Hotwire an old electric trolling motor?

    Quote Originally Posted by Favorite View Post
    They do electric a little different down in Texas

    You might also look into how they used to control fans back in the twenties. And railroad locomotives. They used different resistors to vary the voltage. You get speed jumps that way but it worked fine and was pretty simple.
    The problem with resistance speed control is it wastes a tremendous amount of power as heat.
    Ratus ratus bilgeous snipeous!

    You must be the change you wish to see in the world."
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  17. #17
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    Default Re: Hotwire an old electric trolling motor?

    If you do junk the motor, don't throw it in the landfill. Take it to the recycling yard and get a buck or two. My local yard paid me $2.55 for a dead microwave. They let customers weigh boat trailers on their drive-on scales for free.
    "George Washington as a boy
    was ignorant of the commonest
    accomplishments of youth.
    He could not even lie."

    -- Mark Twain

  18. #18
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    Default Re: Hotwire an old electric trolling motor?

    Quote Originally Posted by Bob Adams View Post
    The problem with resistance speed control is it wastes a tremendous amount of power as heat.
    No, this is not necessarily true. If you control the voltage through the field you won't be wasting doodly.

    But if it's a permanent magnet motor then that can't work
    Last edited by Favorite; 12-22-2018 at 09:51 PM.

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