This workshop manual covers the Volvo Penta MD21A, MD32A, AQD21A, and AQD32A marine diesel engines. These 4-cylinder, 4-stroke diesel engines are designed for reliable performance in marine applications, featuring indirect cooling systems and naturally aspirated aspiration. The MD21A and AQD21A models offer approximately 20-25 horsepower from their 2.1-liter displacement, while the MD32A and AQD32A provide 30-35 horsepower from their 3.2-liter displacement. These engines are engineered for durability and efficiency, making them suitable for a range of vessels. This comprehensive repair manual provides essential information for the maintenance and servicing of your Volvo Penta engine. It details scheduled service intervals, fluid capacities, and recommended fluid types, including engine oil and coolant specifications. The manual also covers technical specifications, troubleshooting guidance, and repair procedures for the engine and associated marine gearboxes. By following the instructions within this manual, owners and technicians can ensure the optimal performance, longevity, and safety of their marine propulsion system.