T500 powering catamaran on long distance adventure

Hi, I’d like to share my experience with powering our mini catamaran with a T500 thruster.

The goal of our holiday adventure was to travel trough several water channels which connects three lovely inland lake here in Switzerland, and all that on top of our mini catamaran powered by a T500 thruster. After a couple of days we reached destination and covered a distance of about 31 nautical miles. Lucky we.

Configuration of prototype

  • Thruster: T500
  • Speed controller: Basic ESC 500
  • Power Switch: Generic 50A anti sparc switch
  • Main battery: DIY 2 x 28Ah 6S Li-ion battery with BMS in a IP68 case
  • Emergency battery: DIY 21Ah 6S Li-ion battery
  • Control System: Arduino MKR WIFI 1010, matrix keypad and OLED dispay


  • Type: Minicat 420
  • Length: 4.2m,
  • Total weight including 2 passengers.: 200kg


  • We controlled the thruster with a constant pulse width signal of 70% of max forward, eg. 1780us
  • This setting delivered a speed over ground of about 2.5 to 2.8 knots
  • We changed battery every 2 hrs. whenever the BMS shut down the energy source because of under voltage. After having completed the planned daily trip we recharged all batteries.


Thruster: The T500 engine was running properly during the entire journey. Everyday the thruster was constantly running for about 3-5 hrs. Nevertheless we encountered some issues with water plants blocking the propeller.

Speed controller: Because the air cooled ESC was positioned within the water resistant plexiglas tube we had some thermal issues. That’s why we could not go further than the mentioned pulse width of 1780us.

Main Battery: Thanks to the water resistant case we did not have any short circuit issues because of water coming in.

Control System: It’s easy to program an Arduino and because there are some improvements waiting to be implemented, I prefer this setup.

Ideas for Improvements

  • Build a second prototype out of an aluminium tube and get ride of the plexiglas version
  • Improved heat conduction for the ESC
  • FOC ESC to reduce thruster noise
  • Replace display with a version based on e-ink display technology
  • Battery fuel gauge to indicate the state of charge



Battery case closed:

Battery case opened:


If you have them, it would be great to see your build notes/pics. You have built a very professional looking unit and we would like to copy it. We are thinking of the same idea for our Happy Cat for those times when the wind dies.

Hi @boris.waldis, this is really cool to see and read about - thanks for sharing! :smiley:

For boating applications it would likely work better to use an unshrouded motor (like our recently released M200), together with a weedless propeller, like is used on our upcoming BlueBoat.

Unfortunately we do not yet have 500-series equivalents of those products.

At high thrust levels the power draw is significant, and the ESC temperatures can get too high without adequate cooling. It would likely help to use a metal enclosure, and/or to make a thermal connection between the ESC heat spreader and the enclosure ends (if you’re using metal ends), and/or to mount the ESC enclosure in the water (at the cost of potentially some extra drag). You’ve already mentioned some of those in your “Ideas for Improvements” section :slight_smile:

This is a neat idea, especially if you’re operating in bright daylight conditions. That said, it may make it more challenging to read in darker conditions if you don’t have some form of light source included as an optional backlight to the display, or pointing at the display from its front.

I’d love to see further updates if/as your project progresses! :smiley:

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