This service repair workshop manual provides comprehensive documentation for Volvo Penta MD21A, AQD21A, MD32A, and AQD32A Marine Diesel Engines. These diesel engines are engineered for marine applications, offering robust performance and reliability. This manual covers all aspects necessary for the service and repair of these units, ensuring their continued optimal operation. The purpose of this manual is to guide owners, mechanics, and technicians through the complete disassembly and reassembly of the engine. It includes detailed step-by-step instructions, hundreds of photos and illustrations, fault tracing guidance, information on special tools, and essential technical data for the engine's various systems, including the electrical system, fuel injection, lubrication, and cooling. All pages are printable for convenient use during maintenance and repair procedures.