This manual covers the Yamaha 4 SD Outboard, a 1990 model designed for marine propulsion. Engineered by Yamaha Motor Corporation, this gasoline-powered, 4-stroke outboard motor represents a commitment to reliable performance on the water. Its robust construction and efficient design make it a dependable choice for a variety of boating applications. This comprehensive English-language Factory Service Manual provides detailed guidance for the maintenance and repair of your Yamaha 4 SD Outboard. It includes step-by-step procedures for disassembly, repair, assembly, and inspection, supported by exploded diagrams. The manual is fully searchable and serves as an essential, handy reference for owners and mechanics to ensure optimal operation and longevity of the outboard motor.