A propeller must remain submerged to deliver continuous thrust, whereas a ship's bow and sides rise and fall more readily in a seaway. Placing the propeller near the rudder also lets the accelerated water improve steering response. This combination made stern installation an early practical conclusion. It also gave screw propulsion an efficiency and range advantage over paddle wheels, whose machinery spends part of each revolution moving through air rather than driving the ship.
Notable Point · 5:17-7:45
Why propellers settled at the stern beside the rudder
Keeping the screw immersed and directing its flow past the rudder made the stern the natural location for efficient, controllable propulsion.