Marine gearbox model MB270A 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.