This workshop service manual provides comprehensive technical information for the Mercury Mariner 40 HP 4-Stroke outboard engine. Designed for reliable performance, this engine leverages advanced 4-stroke technology to deliver consistent power output. Its water-cooled system ensures efficient operation under various conditions, making it a dependable choice for a range of marine applications. The engine features a standard forward, neutral, and reverse gear selection for versatile maneuverability. This manual serves as an essential resource for maintaining and repairing the Mercury Mariner 40 HP 4-Stroke. It details routine service procedures, including recommended intervals for oil changes, impeller replacement, and spark plug maintenance. Technical specifications, lubrication requirements, and fuel system details are thoroughly covered to assist owners and technicians. By following the guidelines within this English-language manual, users can ensure the longevity and optimal performance of their outboard engine.