Modifying commercial boat motor systems


Hello, I would like to start this section in order to discuss possibilities of modifying commercially available boat/trolling motors. There are a few ones available which have features we require:

  • brushless
  • stepless speed control
  • higher power

In most cases we probably need to change the

  • propeller (increase pitch),
  • add remote control
  • add / improve safety systems
  • maybe exchange the ESC in order to deal with LiPos instead of PB-batteries

I expect the prices to go down in the future. Also more brushless systems might be available then.

Most of them might not feasable for high speed demands. If someone, like me, is going for slow foils for wave application, then these ones might be worth evaluating.

Here are some examples:
Haswing Protruar 2.0

  • 24V
  • (too) simple safety system (pin connected to rope, which reduces RPM when disconnected)
  • price Germany: 650€ or $463 in the US
  • 110lbs

Rhino BLx 70

  • 12 V
  • price 400€
  • S-Mode -> more power for short time --> get the board out of the water
  • 70lbs

Explosion Drawing on page 16

Torqeedo Ultralight 403

  • comes with bateries & safety pin
  • applies prop v9/p350 --> needs efficient foil / low speeds


More powerful and expensive:
Caroute N300

  • as full motor or as DIY
  • Maximum thrust: 160 pound
  • Input power:2100W
  • Maximum efficiency:65%
  • Volts:48V
  • Maximum current:43Amp
  • Maximum propeller speed:1500 RPM
  • Shaft: Stainless steel, standard length 42”


More data from Rhino BLx70:

  • Prop Diameter: 25cm
  • Pitch: about 27.5cm (1.1xDiameter)
  • Engine Diameter 80mm with casting about 83mm
  • pretty heavy. The overall unit has a weight of 12kg, most of it comes from the engine and metal casting

Power table given in manual:

  • max Power 64.1A at 776W and 1342rpm
    -> hence without slip there would be a max speed of 22km/h (0.275/1000*60min * 1342=22km/h, actual max speed would be less)
  • big diameter, lots of drag would lead to a lot of slip. 776W would require a very efficient foil and streamline engine housing body


  • Seems not be made for use in sea/saltwater, since they give no guarantee for it then
  • very heavy and huge housing
  • 12V not (easily) achievable with x3.7V batteries
  • might be worth trying for somebody without salt water and slow/huge foils. I don’t like the big nacelle diameter.


Here’s another possibility made by Minn Kota. 160 lbs thrust. $1,250


Funny how I thought these were an ideal starting point just from the perspective of not reinventing the wheel by finding commercially sold products made by reputatble companies that need to keep working for years at a time to stay in business…a $400 gear is simply not possible on this budget!