This Service Repair Manual (WSM) covers the Yanmar 3YM30, 3YM20, and 2YM15 marine diesel engines. These engines are engineered for reliability and performance in marine applications, featuring indirect cooling and indirect injection fuel systems. The Yanmar 3YM30 offers up to 29 PS, the 3YM20 up to 20 PS, and the 2YM15 up to 14.5 PS, all at 3200 RPM. Their robust construction and forced lubrication systems ensure durability for demanding maritime use. This comprehensive manual provides detailed information essential for the maintenance and repair of your Yanmar marine diesel engine. It includes step-by-step repair instructions, clear illustrations, and wiring diagrams covering all aspects of repair and diagnostics. Routine maintenance procedures and general service intervals are also outlined, empowering owners and technicians to keep these engines operating at peak efficiency and longevity.