This Service Repair Manual covers the Mercury Mariner Optimax series engines, available in 135 HP and 150 HP variants. These 2-stroke V6 engines, featuring Direct Fuel Ejection (DFI) and a displacement of 153.2 cu. in. (2.5 Liters), are engineered for robust performance and reliability. This manual is designed to provide comprehensive information for maintaining and repairing these powerful marine engines. The purpose of this manual is to offer detailed, step-by-step repair procedures, preventative maintenance schedules, and troubleshooting guides. It includes clear, zoomable illustrations and diagrams, such as exploded views and component breakdowns, to assist owners, mechanics, and technicians. This resource is essential for ensuring the optimal performance and longevity of your Mercury Mariner Optimax engine.