This workshop service manual covers the Mercury Mariner 90 HP Outboard engine, a gasoline-powered, water-cooled outboard drive unit designed for marine propulsion. Engineered for reliability and performance, this outboard motor features a CDI ignition system and a transmission with forward, neutral, and reverse gears. It is intended for use in various marine applications where dependable power and efficient operation are paramount. This comprehensive manual provides detailed information essential for the maintenance, repair, and servicing of your Mercury Mariner 90 HP Outboard. It includes procedures for lubrication, service schedules, and technical specifications, ensuring optimal performance and longevity. The manual is designed to assist owners, mechanics, and technicians by offering clear instructions and guidance, assuming a general understanding of marine engine practices.