Waterproof High-torque Servo SER-120X, multi-turn, BLDC motor


Digital, waterproof servo, submersible up to 100 meters Programmable rotation up to 7 turns or continuous rotation Brushless motor and magnetic encoder. SKU: SER-1207

Delivery time: 10 - 14 business days


Blue Trail Engineering’s SER-120X is the ultimate underwater servo for small robotic applications. Unlike any other servo in its class, it can be programmed to provide up to 7 turns of rotation with position control or continuous rotation with speed control. The SER-120X features a brushless motor and magnetic encoder, eliminating the most common causes of servo failure. Ideal for Autonomous Surface Vehicles as well as Remotely Operated Vehicles, the SER-120x provides reliable, long-term actuation at depths up to 100 meters.


The SER-120x is based on the Hitec HSR-M9382TH digital servo. Blue Trail integrates a modified HSR-M9382TH into a corrosion-resistant, depth-rated Delrin® housing with a ball-bearing-supported titanium output shaft and nitrile quad-ring shaft seal.


  • Submersible up to 100 meters
  • Programmable up to 7 turns of rotation or continuous rotation*
  • Brushless motor
  • Magnetic encoder
  • Compact size
  • Low power draw
  • Engineered for months of exposure in seawater or fresh water
  • Corrosion-resistant titanium output shaft, Delrin® enclosure
  • Standard R/C PWM interface
  • Servo arms included
  • Square output shaft for easy integration

The SER-120X utilizes the compact and reliable Cobalt 3-pin dry-mate bulkhead connector, compatible with Cobalt Series cables from Blue Trail Engineering.  Custom connection options are also available.


NOTE: Because this servo is capable of more than 1 full turn, it does not have an absolute encoder on the output shaft and does not remember its absolute position when power is cycled. This can be problematic if the servo is being used in a multi-turn application. For example, if the servo is moved 2 turns clockwise and power is then cycled, the servo will move another 2 turns clockwise (it does not remember that it had already moved 2 turns before the power was cycled). The best way to handle this is to center the servo before turning it off.


* By default, this servo travels approximately 1/2 turn.  If you require increased travel or any other changes to the servo’s programmable parameters, we will happily program the servo per your specifications.  Simply email us after placing your order.

Additional information

Weight 0,7 kg