This manual covers the BY Series Marine Diesel Engine, designed for marine propulsion. Engineered for reliability and performance, these diesel engines are built to meet the demanding requirements of maritime operations. This operation manual provides comprehensive information for the 4BY and 6BY models, ensuring optimal function and longevity for your marine diesel engine. The purpose of this English-language operation manual is to guide users through the safe and effective operation, maintenance, and inspection of the BY Series Marine Diesel Engine. It details handling precautions and includes information pertinent to the warranty for the USA. This searchable and printable document is designed to be a valuable resource for owners and technicians alike, facilitating proper care and upkeep of the engine.