The YANMAR 3YM20 is a robust 3-cylinder, water-cooled, 4-cycle diesel engine designed for marine applications. Engineered for reliability and efficiency, this engine offers a displacement of 1.267 liters and delivers a rated power output of 15.1 kW (20.5 PS) at 3200 RPM. Its robust construction and advanced design ensure dependable performance in demanding marine environments, making it a trusted choice for various vessel types. This Factory Service Repair Manual provides comprehensive guidance for the YANMAR 3YM20 marine diesel engine. It covers essential maintenance procedures, including recommended intervals for oil and filter changes, fuel filter replacement, and impeller service. Detailed technical specifications, fluid capacities, and troubleshooting information are also included, empowering owners, mechanics, and technicians to effectively maintain, service, and repair the engine, ensuring its longevity and optimal operation.