For surface running, the boats were powered by a single 12-cylinder  Vickers petrol engine that drove one propeller shaft. When submerged the propeller was driven by a  electric motor.
During surface cruising, the boats utilized a single 12-cylinder Vickers petrol engine connected to a single propeller shaft. In contrast, when submerged, the propeller was propelled by an electric motor, highlighting the dual propulsion system.