This manual covers the YANMAR SY Series Marine Inboard Engine, a diesel-powered internal combustion engine designed for marine propulsion. YANMAR engines are recognized for their robust engineering and reliability, providing efficient and dependable performance for a wide range of marine applications. This series exemplifies YANMAR's commitment to quality and innovation in the marine industry. The purpose of this Service Repair Manual is to provide comprehensive guidance for the maintenance, repair, and technical understanding of the YANMAR SY Series engine. It includes detailed procedures, specifications, and troubleshooting information essential for owners, technicians, and mechanics to ensure optimal operation and longevity of the marine propulsion system. By following the instructions within this manual, users can effectively manage all aspects of the engine's service life.