This Service Repair Manual covers the Yanmar 1SM, 2SM, and 3SM models, designed for robust performance and reliability in various applications. These engines, built with Yanmar's commitment to engineering excellence, offer dependable power and efficiency. While specific model years are not listed, this manual encompasses the necessary information to understand and maintain these versatile internal combustion engines, which are implied to be diesel-powered. The purpose of this manual is to provide comprehensive guidance for the maintenance, repair, and troubleshooting of Yanmar 1SM, 2SM, and 3SM engines. It details essential procedures including engine disassembly and reassembly, servicing, periodical checks, and countermeasures for common engine troubles. Furthermore, it includes a list of approved oils and information on fuel and lubricating oil, enabling owners and technicians to make informed decisions, save time, and ensure the optimal performance and longevity of their Yanmar engines.