Phil Budne's Javascript version of Lee Shuster's boat speed Calculator using Clark Roberts' formula.

Hull Efficiency factors:

Hull Factor Notes
Evinrude Gull-Wing 160-180 (hull performs better under load)
Moderate Vee Bottom 180
Classic Whaler Tri-Hull 200
Flat Bottom 220

Engine Adverized Power (HP)
Empty Hull Weight & Engine (lbs)
Number of People @... 170 lbs each
Additional Fuel and Gear (lbs)
Altitude above sea level (ft)
Hull Efficiency (168 to 220)
Gross (wet) Weight (lbs)
Effective prop-shaft HP
Calculated Top speed (MPH)