If the speed necessary for reaching port at a designated time is 16.8 knots and the pitch of the propeller is 22.3 feet, how many revolutions per minute will the shaft have to turn, assuming a 4% negative slip?

Correct Answer: Option C — 73 RPM

Calculate the required speed through the water by adjusting for slip. With a 4% negative slip, the propeller advances further than the theoretical pitch distance. Using the formula RPM = (Speed × 6080) / (Pitch × 60 × (1 - slip)), the shaft must turn at 73 RPM to maintain 16.8 knots.