What does a propeller do in a boat?

The propeller is a crucial component of a boat's propulsion system. Its primary function is to convert the engine's rotational energy into thrust, which propels the boat forward or backward in the water. When the propeller rotates, it creates a pressure difference between the front and rear sides of the blades. This pressure difference generates thrust, allowing the boat to move.

Understanding that the propeller is specifically designed to push water in one direction, while itself turning, helps clarify why it is not responsible for securing the hull, steering the boat, or measuring water depth. A boat's hull is secured through its design and materials; steering is usually influenced by the rudder or wheel; and depth measurement is typically achieved through devices like depth finders, not a propeller.