If the speed necessary for reaching port at a designated time is 23.7 knots and the pitch of the propeller is 20.8 feet, how many revolutions per minute will the shaft have to turn, assuming a 7% negative slip?

Correct Answer: Option A — 108 RPM

Negative slip occurs when the vessel speed exceeds the theoretical speed of the propeller. Calculate required speed in feet per minute (23.7 knots * 6076.1 / 60 = 2400.06 ft/min). Divide by pitch (20.8 ft) and adjust for 7% negative slip (divide by 1.07) to yield 108 RPM.