This manual covers the Yanmar GM Series Marine Diesel Engines, including models 1GM(10L), 2GM(F)(L), 3GM(D)(F)(L), and 3HM(F)(L). These engines are known for their robust construction and reliable performance in marine applications. The GM Series offers a range of power outputs from 10 HP to 30 HP, with displacements varying across the models to suit different vessel requirements. This comprehensive service manual provides detailed information for maintaining and repairing these dependable marine diesel engines. The purpose of this English-language Factory Service/Repair/Workshop Manual is to equip owners, mechanics, and technicians with the necessary knowledge to perform all maintenance and repair procedures. It includes step-by-step instructions, highly detailed exploded diagrams, and diagnostic capabilities for all engine systems, including the basic engine, fuel, governor, intake and exhaust, lubrication, cooling systems, and reduction gears. All pages are printable, ensuring accessibility for on-site reference and use.