This operation manual covers the Yanmar 1GM10, 2GM20(F), 3GM30(F), and 3HM35(F) marine diesel engines. These engines are engineered for reliable marine propulsion, utilizing diesel fuel to deliver consistent performance. Yanmar is recognized for its commitment to quality and durability in marine applications, ensuring these engines are built to withstand the demands of maritime use. Their robust design and efficient operation make them a trusted choice for boat owners and operators. This manual provides comprehensive guidance for the operation and maintenance of your Yanmar marine diesel engine. It details essential information including engine specifications, installation procedures, operational methods, and storage recommendations. Furthermore, the manual offers valuable troubleshooting advice, covers fuel and lubrication requirements, and outlines periodic maintenance schedules. By following the instructions within this English-language document, owners and technicians can effectively maintain the engine's performance, ensure longevity, and address potential issues promptly.