This service repair manual covers the Mercury Mariner 3.0 HP outboard motor. This 2-stroke, water-cooled engine features a CDI ignition system and carburetor fuel delivery, designed for reliable performance. It utilizes a pre-mix lubrication system with a 50:1 gasoline to oil ratio and is operated via a tiller handle with a manual recoil starter. The outboard drive system is engineered for efficiency and durability in various marine applications. This comprehensive manual provides essential information for maintaining and repairing your Mercury Mariner outboard motor. It details routine maintenance procedures, including specific gearcase oil requirements and fuel mixture ratios. Technical specifications, operational guidance, and troubleshooting steps are included to ensure optimal performance and longevity. This guide is an invaluable resource for owners and technicians alike.