This manual covers the Yanmar 3TNV and 4TNV series of Industrial Diesel Engines, designed for industrial applications requiring reliable diesel power. These engines are known for their robust engineering and dependable performance, making them a preferred choice for various demanding tasks. The comprehensive coverage within this service repair manual ensures that owners and operators can understand and maintain these powerful engines effectively. The purpose of this English-language service repair manual is to provide detailed guidance for the maintenance and repair of the specified Yanmar industrial diesel engines. It includes essential information on general engine operation, inspection and adjustment procedures, troubleshooting common issues, and step-by-step instructions for disassembly, inspection, and reassembly of engine components. Furthermore, it covers critical systems such as lubrication, cooling, fuel injection, turbocharging, starting, and electrical systems, along with service standards and tightening torques, making it an indispensable resource for both do-it-yourself enthusiasts and professional mechanics.