Hi @Adil -
No lubrication is required - DO NOT USE WD40!
The T200 and M200 thruster are lubricated by the water they are used in, and should not be run dry in air for more than a few seconds (ideally at low speed.)
Besides thoroughly rinsing with fresh water, you may want to occasionally disassemble the unit, and wipe the rotor and stator to remove any magnetic sandy particles that may have accumulated, and inspect the rotor for signs of damage to the coating that can lead to rust.
IF you’re not operating in areas with sediment, no maintenance is required! The only component that may wear out eventually is the sheave bearings at the top and bottom of the motor stator - reach out via our support form if you ever have issues with these. Thanks!