The YANMAR 3YM20 is a marine diesel engine designed for a variety of maritime applications. This engine is recognized for its robust construction and reliable performance, making it a trusted choice for boat owners and operators. Its engineering emphasizes durability and efficiency, ensuring consistent operation in demanding marine environments. The YANMAR 3YM20 represents a commitment to quality in marine propulsion systems. This workshop service repair manual provides comprehensive guidance for the YANMAR 3YM20 marine diesel engine. It covers essential areas including periodic maintenance schedules, detailed step-by-step repair instructions, troubleshooting common issues, and complete overhaul procedures. The manual also includes wiring diagrams to aid in diagnostics and repairs. Its purpose is to empower both professional technicians and DIY mechanics with the knowledge required to maintain and repair the engine effectively, ensuring its longevity and optimal performance.