This manual covers the Yanmar 4JH2 Series Marine Diesel engines, including the 4JH2E, 4JH2E-TE, 4JH2-HTE, and 4JH2-DTE variants. These marine diesel engines are engineered for reliability and performance in demanding maritime applications. The series is known for its robust construction and efficient operation, making it a trusted choice for various marine vessels. This document provides comprehensive information to ensure optimal functioning and longevity of your Yanmar engine. The purpose of this service repair manual is to provide detailed guidance for the maintenance, diagnosis, and repair of the Yanmar 4JH2 Series engines. It includes extensive information on engine specifications, fuel and cooling systems, lubrication, intake and exhaust, electrical systems, and engine components. Furthermore, the manual offers detailed procedures for disassembly, reassembly, engine restoration, and rebuilding, along with a troubleshooting guide and preventative maintenance instructions. This resource is essential for owners, mechanics, and technicians to effectively maintain and service their Yanmar marine diesel engines.