This manual covers the Mercury Mariner Optimax, a first-generation outboard motor produced from 1998 to 1999. Engineered with Direct Fuel Injection (DFI) two-stroke technology and a water-cooled system, this model delivers 135 horsepower. Its robust design and reliable performance make it suitable for a variety of marine applications. Key features include a CDI ignition system and a power trim and tilt mechanism, ensuring efficient operation and user control on the water. The purpose of this comprehensive Factory Service Repair Manual is to provide detailed information for the maintenance and repair of your Mercury Mariner Optimax. It covers essential procedures, technical specifications, and troubleshooting guidance for owners, mechanics, and technicians. Within these pages, you will find information on lubrication, fuel system servicing, electrical components, and more, all designed to help you keep your engine in optimal condition and ensure its longevity.