This manual covers the Yanmar 1GM, 2GM, 3GMD, and 3HM series marine diesel engines. These engines are designed for reliable marine propulsion, utilizing indirect injection diesel technology. Yanmar engines are recognized for their robust engineering and dependable performance in marine environments. This documentation provides essential information for the operation and upkeep of these units. The purpose of this English-language user manual is to guide owners and technicians through the maintenance, inspection, and adjustment procedures for the Yanmar marine diesel engines. It includes detailed diagrams for the cooling, fuel, oil, and electrical systems, along with information on routine inspections and recommended service intervals. This manual serves as a comprehensive resource for ensuring the optimal performance and longevity of your Yanmar engine.