This service shop repair manual covers the Yanmar 2GMFY and 3GMFY marine diesel engines. These engines are designed for reliable performance in marine applications, featuring direct injection fuel systems and either raw water or indirect cooling configurations. The 2GMFY model is a two-cylinder engine with a displacement of approximately 0.774 L, while the 3GMFY is a three-cylinder engine with a displacement of approximately 1.161 L. Both models are equipped with inboard marine gearboxes. This manual provides comprehensive guidance for the maintenance, servicing, and repair of your Yanmar marine diesel engine. It details essential procedures such as scheduled filter replacements, belt inspections, and fluid level checks, along with troubleshooting steps to diagnose and resolve common issues. By following the instructions within this English-language manual, owners and technicians can ensure the optimal performance and longevity of their Yanmar 2GMFY or 3GMFY engines.