This repair manual covers the Yanmar 6LY3-ETP, 6LY3-STP, and 6LY3-UTP marine diesel engines. These inline 6-cylinder diesel engines are engineered for reliable marine propulsion, offering robust performance and durability for demanding maritime applications. Yanmar's commitment to quality ensures these engines are a trusted choice for a wide range of vessels. This comprehensive manual provides essential information for maintaining and repairing your Yanmar marine diesel engine. It details routine maintenance procedures, engine removal and installation, and covers critical systems including fuel, lubrication, cooling, transmission, steering, and electrical systems. Advanced troubleshooting guidance is also included, making this manual an indispensable resource for owners, mechanics, and technicians.