This Service Repair Manual covers Mercury Mariner OptiMax outboard engines, specifically models with 115, 135, 150, and 175 horsepower, manufactured from the year 2000 onwards, starting with serial number OG960500. These engines feature Direct Fuel Injection technology and are engineered for reliable performance. The manual encompasses a range of engine variants and is designed to support the maintenance and repair of these robust marine propulsion systems, including their standard and counter-rotating gear housings, power trim systems, and cooling mechanisms. The purpose of this manual is to provide comprehensive guidance for the repair, service, restoration, and maintenance of your Mercury Mariner OptiMax engine. It includes detailed procedures, troubleshooting assistance, technical specifications, and safety guidelines. With clear, step-by-step instructions, illustrated with diagrams and exploded views, this manual is an essential resource for professional technicians, mechanics, workshops, and DIY enthusiasts. It covers all aspects of the engine, from electrical and fuel systems to component breakdowns and part numbers, ensuring that users can effectively diagnose, repair, and maintain their engines for optimal performance and longevity.