This workshop service repair manual covers the Mercury Mariner outboard engine, specifically models equipped with the 3.0L Marathon engine package. Designed for reliable performance on the water, these engines are known for their robust engineering and power output, typically ranging from 135 to 200 horsepower for this displacement. The 3.0-liter V6 configuration, utilizing a water-cooled system and an oil-based lubrication system, provides efficient propulsion for a variety of marine applications. This comprehensive manual provides essential information for the maintenance, service, and troubleshooting of your Mercury Mariner outboard. It details routine maintenance procedures, including recommended fuel types and lubrication specifics, alongside technical specifications and diagnostic guidance. By following the procedures outlined within this English-language resource, owners and technicians can ensure the continued optimal performance and longevity of their Mercury Mariner 3.0L Marathon engine.