M200 Motor Usage Guide

By Kevin


The M200 Motor is a brushless electric motor for use underwater. It is pressure resistant and ruggedized against harsh ocean conditions. Many of the motor’s components are used in the T200 Thruster.


Do not operate the motor for extended periods out of water. The bearings are lubricated by the water and vibration and noise will be greater when dry.

Always practice caution when you’re working with electricity in water and with the spinning blades of the propeller. Keep body parts away from the motor to avoid injury.

A slight clicking noise is normal, especially when operated dry. It is caused by slight movement of the shaft in the plastic bearings.


The M200 uses the flow of water to cool itself during operation. Ensure that the cooling holes on the top of the rotor and the gap between the stator base and rotor allow water to circulate.

The M200 Motor is easy to install in many different applications. It was designed with mounting holes that are identical to those found on many common brushless motors.

2D Drawing showing M3 hole spacing

2D Drawing showing M3 hole spacing

The M200 also has a flexible cable orientation that can be adjusted for flush or inline mounting.

Cable mounting orientation options

Cable mounting orientation options


The motor requires a brushless electronic speed controller (ESC). Checkout our Basic ESC product page for more information.

Connecting to an External ESC

The motor has a cable containing three wires. These three wires must be connected to the three motor wires on the electronic speed controller (ESC). The order does not matter, but if the motor direction is the reverse of what is desired, switch two of the wires.


Do not operate the motor for extended periods out of water. The bearings are lubricated by the water and vibration and noise will be greater when dry.

Clicking Noise

If you hear a clicking noise during operation, especially when operating in air, do not be alarmed. It’s normal.

The motor uses solid plastic bushings and due to the tolerances of the bushings and motors shafts, the shaft can move slightly in the bearing. The noise is drastically reduced or eliminated when operated in water. The water acts as a lubricant for the bearings and smooths operation.

Care and Maintenance

During normal use:

  • Rinse with fresh water after use in saltwater to minimize the accumulation of salt deposits.
  • Rinse after operating in sandy environments to remove sand particles.

If operated for extended periods in the water:

  • Occasionally clean biological fouling and mineral deposits from the motor or performance may be impacted.


Occasionally it may be necessary to disassemble the motor. Here is a quick guide on how to do so!

M200 Motor Disassembly/Re-Assembly
Quickly disassemble an M200!


The motor does not start

This is usually an issue with the proper commands being sent to the ESC. Please see the ESC documentation for instructions on how to operate the ESC properly.

The motor does not start but the rotor tries to move.

This can be caused by a disconnected motor wire or a short between motor wires. Check that all three motor wires are connected and not shorting. To do this, check resistance of each phase pair in the motor. Each motor wire phases pair (Blue/green. blue/white, green/white) should read the same resistance within 0.1-0.2ohms or so. If no connection is read or one pair has significantly higher resistance, your motor has a fault. Please e-mail [email protected] if this fault is found.

The motor is jammed when turned by hand.

This can be caused by something jamming the propeller or by major internal damaged caused by overheating, short circuits, or heavily worn bearings. Please disassemble the motor and inspect for damage or blockage.


For all the engineers out there, here’s some more info.

Test Results

Check out the test results section for the T200 Thruster, which shares most of the same components as the M200.

Quality Control

We perform the following tests on every motor before they are shipped.

  • Spin Test. The motor is operated in air across the entire speed range to ensure that it operates correctly.
  • Visual Inspection. Each motor is inspected for visual issues or damage.



Kevin is the Applications Engineer at Blue Robotics. He has a love for marine robotics and explorations and was one of Blue Robotics' first Kickstarter backers in 2014! Since then he's joined our team and helps fellow explorers around the world use Blue Robotics products to accomplish their missions.