This manual covers the Mercury Mariner 90 HP Outboard, a robust water-cooled engine designed for marine applications. Featuring a 4-cylinder, 1596 cc displacement with a 9.0:1 compression ratio, this outboard delivers 90 HP through a fuel-injected system and a CDI ignition. Its engineering emphasizes reliability and performance, with a forward-neutral-reverse gear system and a typical weight of approximately 158 kg. This engine is built to provide dependable power for various boating needs. The purpose of this Service Repair Manual is to provide comprehensive guidance for the maintenance, repair, and technical understanding of the Mercury Mariner 90 HP Outboard. It details essential procedures, troubleshooting steps, and technical specifications, including engine oil capacity, recommended oil types, fuel requirements, and charging system output. This manual is an indispensable resource for owners, technicians, and mechanics to ensure optimal performance, longevity, and safe operation of the outboard motor.