Wind Pressure in lb/ s ft = 0.004 x MPH (multiply knots x 1.151 to get MPH.
HP lost to wind pressure = ( Wind pressure lbs x boat speed in Kts x200) divided by 33,000. Must estimate the total frontage. ie. 10 foot beam x 5 feet freeboard = 50 sq ft. 6 ft x 8 ft deck house = 48 sq ft = totat 98 sq ft.
Total wind pressure - 98sq ft x 0.004 x 28 squared = 288lb.
(288lbs x 25 kts x 200) divided by 33,000 = 43 HP lost to wind pressure