This service repair manual covers the Yanmar 6SY-STP2, 6SY655, and 8SY-STP marine engines. These engines are engineered for demanding marine applications, offering robust performance and reliability. Their design prioritizes durability and efficiency, making them a trusted choice for various maritime operations. This manual provides comprehensive information to ensure these engines operate at their peak potential. The purpose of this manual is to provide detailed guidance for the repair and maintenance of Yanmar marine engines. It encompasses a wide range of topics, including safety precautions, general service information, periodic maintenance schedules, and in-depth procedures for the engine, fuel system, cooling system, lubrication, turbocharger, starter motor, alternator, and EMS. The manual is designed for both do-it-yourself owners and experienced mechanics, offering easy-to-read text, high-quality diagrams, and step-by-step instructions to facilitate effective troubleshooting and repair.