This Service Workshop Manual covers Mercury 45-225hp Outboard engines manufactured between 1972 and 1989. These engines are known for their robust engineering and reliability, offering dependable performance for a wide range of marine applications. The manual details various engine configurations, including Inline 3, Inline 4, Inline 6, and V6 models, equipped with diverse ignition and fuel systems such as Lightning Energizer Ignition, Distributor-type CD ignition, Flywheel CD ignition, Distributor-less ignition, Thunderbolt CD ignition, and Electronic Fuel Injection (EFI). The purpose of this manual is to provide comprehensive guidance for the maintenance, troubleshooting, and repair of your Mercury outboard engine. It includes detailed procedures for lubrication, tune-ups, and storage, covering tasks like compression testing, spark plug replacement, fuel system service, and electrical system checks. Furthermore, the manual offers extensive troubleshooting information for starting, charging, ignition, fuel, and engine systems, alongside essential technical data including torque specifications, fastener information, lubricant recommendations, and wiring diagrams. This resource is designed to assist owners, mechanics, and technicians in keeping their engines operating at peak performance and longevity.