What is the primary function of a ship's propulsion shaft?

What is the primary function of a ship's propulsion shaft?

• A. To steer the ship
• B. To provide power to the propeller
• C. To pump bilge water
• D. To supply electricity

Answer: (B)

The propulsion shaft’s main role is to transfer the engine’s rotational power to the propeller, turning engine torque into thrust that pushes the hull through the water. It runs from the propulsion gear or crankshaft through the stern tube to the propeller hub, supported by bearings and sealed to keep water out. The engine’s speed is usually reduced by gears so the propeller spins at an efficient rate, and the shaft simply conveys that controlled rotation to the propeller. Steering is handled by the rudder and steering gear, not the shaft, while bilge pumps and electrical power come from separate systems. So providing power to the propeller captures what the shaft actually does.

The propulsion shaft’s main role is to transfer the engine’s rotational power to the propeller, turning engine torque into thrust that pushes the hull through the water. It runs from the propulsion gear or crankshaft through the stern tube to the propeller hub, supported by bearings and sealed to keep water out. The engine’s speed is usually reduced by gears so the propeller spins at an efficient rate, and the shaft simply conveys that controlled rotation to the propeller. Steering is handled by the rudder and steering gear, not the shaft, while bilge pumps and electrical power come from separate systems. So providing power to the propeller captures what the shaft actually does.