This service repair manual covers the Yamaha 20C Outboard, a 2-stroke, water-cooled engine designed for reliable performance. With a displacement of 326 cc (19.9 cu in) and a power output of 20 horsepower at 5000 RPM, this outboard is engineered for a variety of marine applications. Its robust construction and efficient design ensure dependable operation, making it a suitable choice for recreational and professional use. This manual provides comprehensive guidance for maintaining and repairing the Yamaha 20C Outboard. It details essential maintenance procedures, including lubrication specifications, fuel-to-oil ratios, and routine checks such as spark plug gap and idle RPM. The manual also addresses common troubleshooting scenarios, covering issues like starting problems, poor performance, overheating, and electrical faults. Technicians and owners will find the technical specifications and step-by-step instructions invaluable for ensuring the longevity and optimal functioning of the engine.