This workshop service repair manual covers YANMAR 6SY-STP2, 6SY655, and 8SY-STP marine diesel engines. These engines are engineered for robust performance, featuring turbocharged, direct-injection, water-cooled, 4-stroke diesel technology. The 6-cylinder models offer 11.7L displacement, while the 8-cylinder variants provide 15.6L. YANMAR engines are recognized for their quality construction and reliability, making them a preferred choice for demanding marine applications. This comprehensive English-language manual provides detailed instructions and technical data essential for maintaining and repairing your YANMAR marine engine. It includes general information, safety instructions, maintenance procedures, tightening torques, troubleshooting guides, and in-depth coverage of engine disassembly, assembly, testing, and adjustments for the fuel, cooling, lubrication, turbocharger, and electrical systems, including wiring diagrams. With step-by-step instructions, detailed illustrations, and diagrams, this manual is designed to assist both DIY enthusiasts and experienced mechanics in ensuring optimal engine performance and longevity.