Marine gearbox model 138 performs the duties of ahead and asterm, engaging and disengaging as well as reduction of speed. It can be coupled with various diesels with applicable torque to form a complete power unit for marine purpose, which is suitable for all kinds of boats navigating in inland rivers or in coasts.

The asterm transmission system can work under continuous and full-power conditions, therefore it can be matched with the diesel with same rotation direction to form the left-hand or right-hand power unit.