This manual covers the Mercury Mariner 30 HP and 40 HP outboard motors manufactured between 1999 and 2003. These 4-stroke, water-cooled engines, featuring a 3-cylinder configuration, are designed for reliable performance in various marine applications. With power outputs of either 30 or 40 horsepower, they offer a balance of efficiency and capability for recreational boating. The engineering quality and inherent reliability of this generation of Mercury Mariner outboards make them a trusted choice for boaters seeking dependable propulsion. The purpose of this comprehensive Service Repair Manual is to provide detailed guidance for the maintenance, repair, and technical understanding of your Mercury Mariner outboard. It includes essential information on routine servicing, such as recommended oil types and capacities, spark plug specifications, and gear lube requirements. Furthermore, the manual offers in-depth procedures for troubleshooting common issues, technical specifications, and safety guidelines. This resource is invaluable for owners, mechanics, and technicians to ensure the longevity and optimal performance of their 1999-2003 Mercury Mariner 30 HP / 40 HP outboard motor.