The present invention features a screw propeller system for use in a machine including a watercraft or an aircraft. The system features two or more screw propellers installed in the machine. Each screw propeller comprises an axle with a spiral blade disposed on the axle, and a tube hub. A differential and disc-brake device is operatively connected to each the first screw propeller and the second screw propeller. The differential and disc-brake device functions to steer the machine.