This service repair workshop manual covers Yanmar Marine Diesel Engines, specifically models 4BY-150, 4BY-180, 6BY-220, and 6BY-260. These engines are engineered for reliable marine propulsion, offering a range of horsepower from 150 to 260. Yanmar is recognized for its robust engineering and commitment to quality, ensuring these diesel engines provide consistent performance and durability for maritime applications. This comprehensive manual provides detailed instructions and guidance for maintaining and repairing your Yanmar marine diesel engine. It covers essential areas including general service information, periodic maintenance, engine systems, troubleshooting, and specific repair procedures for components like the fuel system, cooling system, lubrication, turbocharger, starter motor, and alternator. Designed for both do-it-yourself enthusiasts and experienced mechanics, this manual offers detailed illustrations and step-by-step instructions to help keep your engine operating efficiently and cost-effectively.