This workshop manual covers Mercury MerCruiser TRS Stern Drive Units produced between 1978 and 1993. These sterndrive units, featuring a dual propeller drive system and hydraulic trim and tilt, were engineered for a wide range of gasoline-powered marine applications, including runabouts, ski boats, cruisers, and performance boats. Designed for high torque applications and integrated power steering, the TRS series offers robust performance and reliable operation, contributing to the exceptional engineering quality and dependability associated with Mercury MerCruiser marine propulsion systems. The purpose of this manual is to provide comprehensive guidance for the maintenance, repair, and operation of your Mercury MerCruiser TRS Stern Drive Units. It details essential procedures such as recommended service intervals, lubrication requirements including specific gear lube recommendations and capacities, and troubleshooting diagnostic procedures for common issues. This English-language resource is intended for owners, mechanics, and technicians, offering the technical specifications and safety guidelines necessary to ensure the continued optimal performance and longevity of these sterndrive units.