The propeller on a vessel has a diameter of 20.2 feet and a pitch of 19.0 feet. What would be the apparent slip if the vessel cruised 367 miles in a 24 hour day (observed distance) at an average RPM of 84?

Correct Answer: Option C — +2.9%

Calculate engine distance: (84 * 1440 * 19) / 6076.1 = 378.1 miles. Slip formula is (Engine Distance - Observed Distance) / Engine Distance. (378.1 - 367) / 378.1 = 0.0293, or +2.9%. Positive slip occurs when the vessel's actual speed is less than the theoretical speed of the propeller through the water.