The speed of advance necessary to arrive in port at a designated time is 15.8 knots. The pitch of the propeller is 20.75 feet. You estimate 5% positive slip. How many RPM must you turn to make the necessary speed?

Correct Answer: Option D — 81.2

Propeller slip equations dictate that speed equals RPM multiplied by pitch and (1 - slip). With 5% positive slip, calculating required RPM for 15.8 knots at a 20.75-foot pitch requires dividing effective speed by pitch distance, yielding 81.2 RPM.