Which component of a Yamaha outboard motor is critical for propelling the boat?

The propeller is the critical component for propelling a boat because it directly converts the engine's power into thrust. When the engine runs, it drives the propeller's blades, which push against the water, generating the forward motion needed to move the boat through the water. The efficiency and design of the propeller significantly impact the performance and handling of the boat.

In contrast, while the engine provides the necessary power to turn the propeller, it is the propeller that actually interacts with the water to create movement. The fuel tank, though essential for storing the fuel that powers the engine, does not contribute to the actual propulsion. Similarly, the steering wheel is important for navigation and control but does not influence how the boat is propelled.