The YANMAR 6LY3 Series represents a line of advanced marine diesel engines, specifically designed for demanding maritime applications. This series includes models such as the 6LY3-ETP, 6LY3-STP, and 6LY3-UTP, each offering robust performance and reliability. Engineered with an inline 6-cylinder, 4-stroke diesel configuration, these engines feature turbocharged and intercooled aspiration for enhanced power delivery. Their precise construction, with a bore of 105 mm and a stroke of 125 mm, results in a displacement of 6.5 liters, providing efficient power output ranging from 380 to 480 mhp depending on the specific model. The YANMAR 6LY3 Series is built for durability and consistent operation in challenging marine environments. This Workshop Service Manual provides comprehensive guidance for the maintenance and repair of the YANMAR 6LY3 Series marine diesel engines. It covers essential operational details, technical specifications, and maintenance procedures, including lubrication requirements, filter types, and fuel system information. The manual details engine dimensions, weight, and power outputs for various models, along with transmission specifications. Its purpose is to assist owners, technicians, and mechanics in performing routine servicing, troubleshooting issues, and ensuring the optimal performance and longevity of their YANMAR engines. An accompanying Operation's Manual is also available for further operational insights.