Rov Thrusters and motor questions



Hi Everyone,

I am new to this forum and have a few questions about an ROV that I will be building this summer. So my first question is about thrusters. I was wondering if I need to waterproof dc motors in order for them to work underwater? If I need to what would be a good way to waterproof them? My final question for now is if use dc motors in my project how many Rpm’s would they need to spin at and how much torque I would need in grams. The ROV I am building will use the same frame as the seafox. It will roughly weigh between 5 and ten pounds.

Thats all for now,



There is some great info on waterproofing thrusters in this thread.

The motors spin between 3000 - 6700 RPM depending on thrust setting.
I can’t remember how much torque the standard motor and prop produces, but it should be on the forum somewhere.


I forgot to mention in my first post that I will be using 12 volt brushed dc motors will this be any different working underwater than a brushless set up? Now with Rpm’s spinning at 3,000-6,700 is that before the motor is submerged or is that the Rpm’s the motor will need to spin at underwater?



The RPM is unloaded in air, as I don’t have a way to measure RPM underwater. Brushed DC motors are very different to brushless and are a bad choice for an underwater motor. Brushed motors need air or a non conductive liquid / gas to operate in and the winding’s will short out if they get water in them. A common approach is to house the DC motors inside the pressure vessel and have sealed shafts to the props outside. But this gives you more places for your ROV to leak and more seals to maintain. I would recommend using brushless motors if possible and do a lot more research if you still plan to use brushed DC.