This factory service repair manual covers the Mercury Mariner 225/250 EFI outboards, specifically the Marathon and SeaPro models from the 3.0 Litre 2-Stroke generation. These engines are engineered for robust performance, featuring electronic fuel injection for enhanced efficiency and power delivery, with options available at 225 HP and 250 HP. Designed for demanding marine applications, these outboards are built with a focus on reliability and durability, ensuring consistent operation in various conditions. This manual applies to serial numbers US 0D280813 and above. The purpose of this comprehensive English-language manual is to provide immediate repair and maintenance guidance. It details essential procedures for keeping your Mercury Mariner engine in optimal condition, covering critical areas such as electrical systems, fuel system, powerhead, mid-section, lower unit, and control linkage. With step-by-step instructions, technical data, diagrams, and parts lists, this resource is invaluable for owners, mechanics, and technicians seeking to perform immediate repairs and routine maintenance effectively.