The Mercury Mariner 150 Magnum III, produced between 1992 and 2000, is a robust 2-stroke outboard engine renowned for its reliable performance. Featuring a 2.0 L inline 4-cylinder configuration, this water-cooled engine delivers 150 horsepower through a carbureted fuel system and CDI ignition. Its engineering emphasizes durability and consistent power output, making it a dependable choice for a variety of marine applications. The Magnum III generation represents a significant advancement in outboard technology, offering enhanced efficiency and operational longevity. This Service Repair Manual provides comprehensive guidance for the Mercury Mariner 150 Magnum III. It covers essential maintenance procedures, including detailed instructions for lubrication, spark plug replacement, and water pump impeller servicing, along with recommended intervals for fuel filter changes. Technical specifications, troubleshooting advice, and information on the outboard gearcase and trim systems are also included. This manual is an indispensable resource for owners, mechanics, and technicians seeking to maintain, repair, and optimize the performance and lifespan of their Mariner 150 Magnum III engine.