This workshop repair manual covers the YANMAR HM/GM Series Marine Diesel engines, specifically the 1, 2, and 3 cylinder generations. These diesel engines are engineered for marine applications, featuring direct injection fuel systems and water-cooling. Their robust construction and reliable performance make them a trusted choice for boating enthusiasts and professionals alike, providing dependable power for a variety of maritime needs. This comprehensive manual is designed to assist owners, mechanics, and technicians in maintaining and repairing YANMAR HM/GM Series engines. It details essential procedures for general maintenance, engine rebuilding, and troubleshooting across key systems including cooling, fuel injection, lubrication, electrical systems, and the governor. The manual also provides technical data, parts diagrams, and information on the clutch and transmission, ensuring all aspects of engine care are thoroughly addressed.