This manual covers the Mercury Mariner Optimax, an early generation outboard motor produced for the 1998 and 1999 model years. Featuring a V6, 150 cubic inch Direct Fuel Injection (DFI) 2-stroke engine, this model delivers 150 horsepower and is water-cooled. Its robust engineering emphasizes reliability and performance, making it a capable choice for various marine applications. The outboard lower unit, equipped with a hydraulic power trim and tilt system, further enhances its operational versatility. This comprehensive Factory Service Repair Manual in English provides detailed information essential for the maintenance and repair of your Mercury Mariner Optimax. It covers critical areas including lubrication with recommended Mercury OptiMax 2-Stroke Oil, specific maintenance intervals for components like spark plugs and water pump impellers, and technical specifications for the fuel and electrical systems. This resource is designed to assist owners, mechanics, and technicians in understanding, servicing, and ensuring the longevity of the engine.