We have found Caroute Motors to be suitable and best value for money.
24 volt version up to 80 Amps giving 160 lbs of thrust at 1500 RPM
We also order specially extra long cables for control levers and extended shaft length for extra depth
They conserve battery power by using PWM (pulse width modulation ) .
They are water cooled by having the motor module under water.
The main problem in use is if they are run fast and get stuck in mud, the resistance causes a rise in current and temperature which can burn out the controller.
The controller can be replaced with a spare, using potting compound.
First you need to open the motor unit and inspect it.
If the rotor is straight, stator and wires good, Inspect the controller. The controller is sealed in back cover.
If the motor controller is damaged due to very high current. Please see instruction below. The sealant is a two-component silicone, this silicone is a kind of elastomer designed for electronic potting applications. QSil 553 or similar good heat-conductive sealant is fine to use. If you or your people have experience of potting electronic parts, you can seal the controller.
The price of a replacement controller is 210USD. The controller freight to Romania is 35USD.