Power calculations.

Planing Boats Power calculation formula : 

Kts = C / (LB/SHP)0.5

so if I want to get the estimated HP of a given boat I can:

SHP = KTS² x LB/C²

for example 

If a given boat, the speed is 28knots 

displacement 12,000 pounds 

we can know C :150

so

Shp = 28x28x12000/150x150

       = 418

consideration of the losses during the process 70%

so 

Shp = 418/70%

       =597 

that means 298hp each engine.