This workshop service repair manual covers the Mercury Mariner 90 HP 3 Cylinder Outboard, produced between 1987 and 1993. This engine features a 3-cylinder in-line configuration, a carburetor fuel system, CD ignition, and an oil injection system. It is water-cooled, equipped with an electric start and power trim, and delivers 90 horsepower. The engineering of this outboard is designed for reliability and performance in marine applications. This comprehensive manual provides detailed step-by-step repair procedures, disassembly and assembly instructions, and cleaning and reinstalling guidelines. It includes critical technical specifications, detailed illustrations, drawings, photos, and wiring diagrams to aid in understanding and maintenance. Troubleshooting guides are also included to assist in diagnosing and resolving issues. This resource is essential for owners, mechanics, and technicians to ensure proper maintenance and repair of the Mercury Mariner 90 HP 3 Cylinder Outboard.