The Mercury Mariner 40 HP is a 2-cylinder, 2-stroke outboard motor renowned for its robust engineering and reliable performance on the water. This model delivers 40 horsepower and features a 726cc displacement, designed for efficient operation with its water-cooled system and CDI ignition. Its fuel delivery is managed by a carbureted system, and lubrication can be handled via oil injection or pre-mix, offering versatility for various operational preferences. The transmission provides forward-neutral-reverse gear selection with a 2.15:1 gear ratio, ensuring responsive control. Available with short or long shaft lengths, this outboard motor is built to meet the demands of diverse marine applications. This Service Repair Manual provides comprehensive guidance for maintaining and repairing the Mercury Mariner 40 HP outboard motor. It covers essential maintenance procedures, including recommended oil types and intervals for critical components like spark plugs and water pump impellers, as well as gear oil capacity. Detailed technical specifications, such as bore, stroke, and ignition system details, are included to aid in accurate diagnostics and repairs. This manual is an indispensable resource for owners, mechanics, and technicians seeking to ensure the longevity, optimal performance, and safety of their Mercury Mariner 40 HP outboard motor.