189. 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 revolutions per minute must you turn to make the necessary speed?

To achieve a speed of advance of 15.8 knots, accounting for 5% positive slip, the propeller must turn at 81.2 RPM. This calculation involves converting the speed of advance to feet per minute, considering the propeller pitch and the effect of slip on the theoretical speed.