Which component is essential for powering a boat?

The propeller is essential for powering a boat because it is the component that translates the engine's mechanical energy into thrust, allowing the vessel to move through the water. When the engine runs, it turns the propeller blades, creating a difference in water pressure on either side of them. This difference generates forward motion, propelling the boat ahead.

Other components listed, while important for various aspects of the boat's functionality, do not directly contribute to its propulsion. The beam is related to the width of the boat, which affects stability and interior space but is not involved in powering it. Cleats are used to secure lines and are important for docking, but they do not contribute to movement. The gunwale serves as the upper edge of the boat's sides and provides structure, but again, it does not play a role in moving the boat through the water. Thus, the propeller stands out as the critical component for powering a boat.