This service repair manual covers the Yanmar Marine Diesel Engine series, including models 4BY-150, 4BY-150Z, 4BY-180, 4BY-180Z, 6BY-220, 6BY-220Z, 6BY-260, and 6BY-260Z. Yanmar engines are recognized for their robust engineering and reliability, designed for demanding marine applications. This manual provides comprehensive guidance to ensure these engines perform optimally and maintain their operational integrity through proper service and repair procedures. The purpose of this manual is to serve as an indispensable resource for owners and technicians alike. It details critical information on safety, general service procedures, periodic maintenance, and in-depth troubleshooting for various engine systems, including the fuel, cooling, lubrication, and electrical systems. With easy-to-read text, high-resolution diagrams, and step-by-step instructions, this manual facilitates efficient and effective maintenance and repair, ensuring the longevity and proper functioning of your Yanmar marine diesel engine.