This manual covers the Yanmar 2YM15, 3YM20, and 3YM30 series marine inboard diesel engines. These engines are engineered for reliability and performance in marine applications, offering robust power outputs ranging from 14 HP for the 2YM15 to 27 HP for the 3YM30. Designed with indirect cooling systems and efficient diesel combustion, they are suitable for a variety of maritime vessels. The series is built to the high standards expected of Yanmar, ensuring durability and consistent operation for demanding marine environments.

The purpose of this service manual is to provide comprehensive guidance for the maintenance, repair, and technical understanding of the Yanmar 2YM15 / 3YM20 / 3YM30 series engines. It details essential information including engine specifications, lubrication requirements, cooling system maintenance, fuel system servicing, and troubleshooting procedures. This resource is intended for owners, technicians, and mechanics, enabling them to perform routine maintenance, diagnose issues, and ensure the optimal performance and longevity of their Yanmar marine engines.