Trolling Motor Shaft Coupler Design

My goal was to find a way to connect trolling motor control systems to a stock Minn Kota Trolling Motor shaft. As you may remember in my first version I used some tubing that I “turned down” with sand paper so it would fit inside the Minn Kota Trolling Motor shaft and fit a 22mm ServoCity coupling. Even though that works I didn’t like the process. Images related to this initial solution can be found HERE

I decided awhile back to base most of my trolling motor control systems on components from ServoCity. ServoCity sells all kinds of mechanical and electrical components that currently best suit my needs. Having said that, almost ALL ServoCity mechanical components accommodate tubing and shaft sizes up to and including 1.000”. The one exception is the ServoCity 1.315” Bore Clamping Hub. This hub is made to fit over 1” Schedule 40 PVC pipe. 

My second version of a coupler between a Minn Kota Trolling Motor shaft and the rest of my control system is based on the ServoCity 1.315” Bore Clamping Hub. The motor shaft has a 1.125” OD which seems to be the same for all ENDURA class trolling motors. I am not sure about other larger Minn Kota trolling motors. Since there is a 0.190” difference between the ID of the clamping hub and the OD of the motor shaft I need to “shim” the motor shaft. I used two layers of 1.250” 3:1 adhesive lined heat shrink tubing. It is very important that when heating the heat shrink that it is done equally from all sides so that final thickness is even. The second layer will take a bit of force to get it over the first layer but it is possible. A bit of spit works like a champ. 😉

It should be noted that this setup is NOT waterproof but some medium wall adhesive lined 2” 3:1 heat shrink tubing will make this setup waterproof.