This workshop service repair manual covers the Yanmar YSM8 and YSM12 diesel marine engines, designed for marine propulsion. These engines are engineered for reliability and performance in demanding marine environments, utilizing diesel fuel for efficient operation. The YSM8 model typically offers 8 horsepower, while the YSM12 model provides 12 horsepower, catering to various vessel needs. Their robust construction and diesel power source ensure dependable service for marine applications. This comprehensive English-language manual provides essential information for maintaining and repairing your Yanmar marine engine. It details critical maintenance procedures, including recommended oil types and capacities, service intervals, and cooling system specifics. Furthermore, the manual offers technical specifications and guidance on troubleshooting common issues, ensuring that owners, mechanics, and technicians have the knowledge to keep the YSM8 and YSM12 engines operating at peak performance and longevity.