Electric Boat Propulsion

The motors of the cats are disability scooter motors welded into a propane tank that is filled with oil in order to prevent water from damaging the motor. This means the motor is not easily accessible should the brushes need replacing.

The power is controlled by a large spring that acts as a potentiometer (like a dimmer switch). The shorter the length of spring the electricity flows through, the more power delivered to the motor.

A more technical but far superior electric motor was made by Mythbuster's Jamie Hyneman:

https://www.youtube.com/watch?v=_EV2qq2-Lck&t=2s

Jeremy Fielding
Jeremy Fielding's entire channel, in particular this introduction to motors playlist, is fucking great! Really chill, thorough guy!

I would recommend starting here if you have some knowledge of how electricity works already. Even if you don't you could stand to learn a lot.

Post Apocalyptic Inventor
This German dude is equally knowledgeable but in my opinion a liiiittle harder to follow. You could still learn a lot, especially if you already know a bit. His video on washing machine motors might be a good starting place