This manual covers Mercury Mariner 25, Marathon 25, and SeaPro 25 outboard engines. These 2-stroke outboard engines deliver 25 horsepower and feature a water-cooled system. The transmission utilizes an outboard gearcase with forward, neutral, and reverse capabilities. Designed for reliable performance, these engines are built with robust engineering to meet the demands of various marine applications. This service repair manual provides comprehensive information for maintaining and operating these Mercury outboard models. The purpose of this English-language service repair manual is to provide detailed guidance for the maintenance, troubleshooting, and repair of Mercury Mariner 25, Marathon 25, and SeaPro 25 outboard engines. It covers essential procedures such as fuel mixture, ignition system maintenance, cooling system upkeep, and transmission servicing. Specific details on oil types, capacities, and replacement intervals are included to ensure optimal engine performance and longevity. This manual is an indispensable resource for owners, mechanics, and technicians seeking to understand and maintain these vehicles.