Rhino VX Internal Wiring

We recently had a Rhino VX electric outboard motor in the workshop and were intrigued to know how the internal wiring was configured to make use of the four wires to give multiple speeds on what seemed a simple pmdc motor.

After removing the two bolts holding the three parts of the motor assembly together, the brush assembly was removed.

Inside the brush assembly there are two coils that are connected to the brushes, it appears that these are voltage dropping resistors and are bonded to the housing for cooling purposes.

The wiring diagram for these coils looks like this…

Feeding 12V to the yellow wire gives low speed, blue gives medium speed, and red gives full speed. This is a simple and cheap way of varying the speed but not the most efficient when running at intermediate speeds as power will be wasted heating up the ocean.