This service repair manual provides comprehensive information for the Mercury Mariner 20 HP Outboard motor. Designed for reliable performance on the water, this gasoline-powered outboard features a water-cooled engine and a CDI ignition system. Its robust construction and efficient design make it suitable for a variety of boating applications. The outboard drive system is equipped with a Forward-Neutral-Reverse (F-N-R) gear selection for versatile maneuverability. This manual covers models with US serial numbers 0G044027 and above, and BE serial numbers 09807909 and above. The purpose of this manual is to guide owners, technicians, and mechanics through the maintenance, repair, and troubleshooting of the Mercury Mariner 20 HP Outboard. It details essential procedures, including lubrication requirements for the gearcase using Quicksilver High Performance Gear Lubricant or equivalent, and specifies the recommended 87 octane minimum fuel. Technical specifications, such as spark plug types (NGK BUHW or Champion L77JC4) and ignition system details, are provided to ensure correct servicing. This guide is an indispensable resource for maintaining the optimal performance and longevity of your Mercury Mariner outboard.