This manual provides comprehensive service and repair information for the Hino W04D marine engine. Designed for reliability and performance in marine applications, the W04D engine is engineered to meet demanding operational requirements. This document details the specific procedures and specifications necessary for maintaining and repairing this engine model, ensuring its continued efficient function. The purpose of this manual is to serve as a definitive guide for owners, mechanics, and technicians. It covers a wide range of topics including engine identification, general precautions, maintenance schedules, detailed inspection and maintenance procedures, special tools, engine body, fuel system, cooling system, electrical system, and troubleshooting. With step-by-step instructions, detailed illustrations, and critical specifications, this manual empowers users to perform diagnostics, repairs, and routine maintenance accurately and effectively.