This workshop service repair manual provides comprehensive information for Mercury MerCruiser GM V8 engines, specifically the 5.0L and 5.7L models, covering the 305 CID and 350 CID displacements. These V8 engines, featuring cast iron blocks and Overhead Valve (OHV) valvetrain, are known for their robust construction and reliable performance in marine applications. While specific production years are not detailed, this manual addresses the core engineering of the GM V8 platform, including its carbureted fuel system, marine closed cooling system, and electronic ignition. The manual is designed to assist users in understanding and maintaining these powerful and durable marine powerplants. The purpose of this manual is to serve as a definitive guide for the maintenance, repair, and troubleshooting of the Mercury MerCruiser GM V8 engines. It covers a wide range of critical systems, including engine removal and installation, electrical systems, fuel and cooling systems, exhaust, and the MerCruiser stern drive. Detailed technical specifications, maintenance schedules, and procedural instructions are provided in English to ensure clarity and accuracy for owners, technicians, and mechanics. By utilizing the information within this manual, users can effectively preserve the operational integrity and longevity of their marine propulsion system.