This manual covers the Mercury Mariner outboard engine models produced between 1987 and 1993. These early Mariner models are known for their robust 3-cylinder, 90 HP 3-cylinder outboard engine configurations, featuring electrical and ignition systems, carburetion, and an oil injection system for reliable performance. The outboard lower unit drive with a gear housing ensures efficient power transfer. Notable performance features include power trim, with variations in its design such as Design I (Side Fill), Design II (Aft Fill), and Single Ram, contributing to the engine's versatility and ease of operation on the water. The purpose of this comprehensive Factory Service Repair Manual is to provide detailed information for the maintenance, repair, and troubleshooting of your Mercury Mariner outboard. It includes step-by-step repair procedures, detailed illustrations and diagrams, and essential wiring diagrams. The manual offers advanced troubleshooting guidance for engine fault symptoms and the electrical system, along with comprehensive technical information. With search functionality and printability options, this English-language manual is an indispensable resource for owners and technicians aiming to maintain optimal engine performance and longevity, potentially saving significant labor costs.