This Service Repair Manual covers the Mariner 40, 45, and 50 HP 4-stroke Bigfoot outboard motors, identified by serial numbers starting from OG 231123. Engineered for marine propulsion, these robust engines are designed for reliability and performance on the water. Their 4-stroke gasoline operation, coupled with a water-cooled system and electronic ignition, ensures efficient and dependable power delivery. The Bigfoot designation signifies enhanced torque and durability, making these motors suitable for a variety of demanding marine applications. This comprehensive manual provides essential information for the maintenance, repair, and operation of your Mariner outboard motor. It details critical procedures, including lubrication, service intervals, and inspection schedules, ensuring your engine performs optimally. Technical specifications, troubleshooting guidance, and safety protocols are thoroughly explained to assist owners, mechanics, and technicians in maintaining the longevity and functionality of the unit. This resource is designed to empower users with the knowledge needed for effective upkeep and repair.