This workshop service repair manual covers Mercury Mariner 30JET HP and 40 HP outboard engines. These gasoline-powered, water-cooled, 4-cylinder outboard engines are designed for marine propulsion, offering 30 HP and 40 HP performance. While specific production years are not detailed, this manual is applicable across multiple model years for these horsepower variants, reflecting Mercury's commitment to reliable marine power. This comprehensive English-language manual provides essential information for the upkeep and repair of your Mercury Mariner outboard. It details service procedures, routine maintenance schedules, and troubleshooting guidance to ensure optimal performance and longevity. Owners, mechanics, and technicians will find the technical specifications and procedural instructions invaluable for maintaining and repairing these engines effectively.