This workshop service repair manual covers Mercury Marine OptiMax outboard engines, specifically models 75, 90, 115, 125, and Pro XS 115, manufactured from 2010 onward, with serial numbers 0T801000 and above. These 3-cylinder, water-cooled engines feature a 1.5L displacement and advanced DFI (Direct Fuel Injection) technology managed by a Propulsion Control Module (PCM). The OptiMax series is engineered for reliable performance and efficiency, incorporating sophisticated systems such as the Guardian Protection System for engine longevity and a Computer Diagnostic System (CDS) for advanced troubleshooting. This comprehensive manual provides essential information for the maintenance, repair, and servicing of your Mercury Marine OptiMax engine. It details critical procedures for engine components, including the powerhead and gear housing assemblies, cooling system, and power trim operation. Furthermore, the manual covers installation guidance for outboard components, electrical and wiring connections, control cable installation, and propeller information. It also includes troubleshooting steps, circuit diagrams, and maintenance specifications, enabling owners and technicians to ensure optimal performance and longevity of the engine.