This workshop service repair manual covers YANMAR 1SM, 2SM, and 3SM marine diesel engines, designed for reliable marine propulsion. These diesel engines are engineered for durability and performance in demanding marine environments. This manual provides comprehensive information to ensure the optimal operation and longevity of your YANMAR marine diesel engine. The purpose of this manual is to provide detailed guidance for the maintenance, repair, and servicing of YANMAR 1SM, 2SM, and 3SM marine diesel engines. It includes procedures for engine disassembly and reassembly, adjustments, periodic checks, troubleshooting common engine problems, and guidance on fuel and lubrication. This resource is intended for owners, mechanics, and technicians to facilitate proper care and efficient repair of these engines.