You must average 16.25 knots to reach port at a designated time. Your propeller has a pitch of 21'08", and you estimate 4% negative slip. How many RPM's must you average to arrive on time?

Correct Answer: Option B — 73 RPM

Negative slip indicates the vessel advances faster than the nominal pitch speed due to hull-propeller interaction. Converting 21 feet 8 inches to decimal feet and applying a 4% negative slip factor yields the required engine speed of 73 RPM.