The calculated speeds listed are approximate and considered accurate on the listed displacement. Changes in displacement (or weight) will modify the figures and will not give the speeds listed. All speeds listed are in knots per hour. To convert to miles per hour, divide by .87. Note that the horsepower is given as SHAFT HORSEPOWER (SHP). Since most motors are listed at BRAKE HORSEPOWER (BHP), it will be necessary to reduce the BHP to SHP. A reliable factor to multiply the BHP by is .70 to determine the SHP. All speeds assume that the proper gear ratio and propeller size is used. For twin engines, divide the SHP figure by two in order to determine horsepower required for each engine.