This manual covers the Yanmar line of Marine Diesel Engines, including models 1GM10, 2GM20, 3GM30, 3HM35, and their variants. These engines are engineered for reliable marine propulsion, utilizing robust diesel technology and offering both direct sea-water and fresh water cooling systems. Their design emphasizes durability and performance, making them a trusted choice for various marine applications. The purpose of this comprehensive 470-page Service Repair Manual is to provide detailed information for the maintenance, repair, and operation of your Yanmar Marine Diesel Engine. It includes in-depth coverage of the fuel system, lubrication system, intake and exhaust systems, electrical system, governor system, reduction and reversing gears, and remote control systems. With clear instructions for disassembly, reassembly, and general operation, this manual serves as an essential resource for owners, mechanics, and technicians to ensure optimal performance and longevity of the engine.