This manual covers the Yanmar QM, GM-HM, 4JH & 4JH2 Series Marine Diesel Engines and Transmissions manufactured between 1975 and 1998. These inboard marine diesel engines and transmissions are engineered for reliable marine propulsion. Yanmar is recognized for its robust engineering and durable products, designed to meet the demanding requirements of marine applications. This comprehensive service and repair manual provides detailed instructions for all repairs, servicing, and troubleshooting procedures. With hundreds of pages of content, including detailed photos, diagrams, step-by-step instructions, and exploded diagrams, this manual is an essential resource for owners, mechanics, and technicians. It ensures the proper maintenance and repair of your Yanmar marine propulsion system.