The propeller on a vessel has a diameter of 20.9 feet and a pitch of 19.6 feet. What would be the apparent slip if the vessel cruised 447 miles in a 23 hour day (observed distance) at an average RPM of 108?

Correct Answer: Option D — +7.0%

Engine distance: (108 * 60 * 23 * 19.6) / 6076.1 = 480.7 miles. Slip: (480.7 - 447) / 480.7 = 0.070, or +7.0%. Positive slip is the standard performance metric when the vessel's actual speed is lower than the theoretical propeller advance, indicating drag or resistance.