This Service Repair Workshop Manual covers Mercury Outboard engines from the 1966-1989 Series. These engines, known for their robust engineering, offered power outputs ranging from 90hp to 300hp and featured various configurations including V6 and Inline engine types. With options for carbureted and fuel-injected systems, CDI and electronic ignition, and water-cooled operation, these outboards were designed for reliability and performance across a wide spectrum of marine applications. The manual provides comprehensive information for maintaining and repairing these versatile marine power units. The purpose of this manual is to serve as a definitive guide for owners, mechanics, and technicians. It details essential maintenance procedures, including tune-ups, timing adjustments, and carburetor service, alongside in-depth troubleshooting for common engine issues such as starting problems and performance diagnostics. Extensive coverage is provided for major repair topics, including the lower unit, tilt and trim systems, and starter systems, supported by numerous high-quality pictures and diagrams. This resource ensures that all aspects of the Mercury Outboard engine, from basic operation to complex repairs, can be addressed effectively.