This manual covers the Yanmar 3YM30, 3YM20, and 2YM15 diesel engines. These engines are known for their robust construction and reliable performance, making them suitable for a variety of applications. The engineering quality of Yanmar ensures durability and efficiency in demanding environments. This service repair manual provides comprehensive information to keep these engines operating at peak performance. The purpose of this English-language, 231-page manual is to serve as a definitive guide for the maintenance, repair, and troubleshooting of the specified Yanmar diesel engines. It includes detailed procedures for general inspection, disassembly and reassembly, component servicing, and specific systems such as intake, exhaust, lubrication, cooling, and electrical. With illustrated instructions and clear explanations, this manual is an essential resource for owners, technicians, and mechanics to ensure the longevity and proper functioning of their Yanmar engines.