This workshop service manual provides comprehensive information for the Mercury Mariner 4 HP 4-stroke outboard engine. Designed for reliability and efficient operation, this engine features a single-cylinder configuration and a water-cooled system, ensuring consistent performance across various conditions. Its robust construction and CDI ignition system contribute to its dependable operation, making it suitable for a range of marine applications. This manual serves as an essential resource for owners, mechanics, and technicians. It details critical maintenance procedures, including recommended schedules for spark plug, water pump impeller, and fuel filter replacement, along with specific lubrication requirements for the engine. Technical specifications, troubleshooting guidance, and general advice for technicians are also covered, empowering users to maintain and repair the Mercury Mariner effectively and ensure its longevity.