This manual covers the Yanmar YSE 8/12 series diesel engines. These single-cylinder, water-cooled engines are designed for various applications requiring reliable power, offering outputs between 8 and 12 horsepower. Known for their robust construction and efficient direct injection fuel systems, Yanmar engines are engineered for durability and performance in demanding environments. This documentation aims to provide comprehensive information to ensure optimal operation and longevity of your YSE series engine. The purpose of this manual is to serve as a complete guide for the operation, service, and repair of the Yanmar YSE 8/12 engines. It details essential procedures, including pre-use preparation, starting and stopping protocols, routine maintenance checks, and fluid management. Specific guidance is provided for adjustments, such as the fuel injection regulator, and identification of parts. This resource is intended for owners, mechanics, and technicians, offering the necessary technical specifications and instructions to maintain the engine's peak performance and reliability.