The YANMAR 6LYA, 6LY2, and 6LY2A Series are robust marine diesel engines designed for demanding maritime applications. These 6-cylinder, 4-cycle, water-cooled engines are engineered for reliability and performance, featuring vertical orientation and advanced systems such as turbocharging. With displacements of 5.184 L for the 6LYA-STP and 5.813 L for the 6LY2-STE and 6LY2A-STP models, these engines provide substantial power for various vessel types. Their robust construction and sophisticated engineering ensure dependable operation in challenging marine environments. This workshop service manual provides comprehensive guidance for the maintenance, repair, and troubleshooting of YANMAR 6LYA / 6LY2 / 6LY2A Series marine diesel engines. It covers all major engine components, including the cylinder block and head, crankshaft, camshaft, fuel injection system, lubrication system, turbocharger, and cooling water system. Additionally, the manual details procedures for the reduction gear and reversing gear systems, as well as the remote control and electrical systems such as the starter motor and instrument panel. With step-by-step instructions, diagrams, and diagnostic support, this manual is an essential resource for owners, mechanics, and technicians to ensure optimal engine performance and longevity.