yes there are several formulas kicking around, along with several charts to give an approximation of:
: prop size and pitch for a known horsepower and rpm of the motor
: if the boat's weight and size are known & you know what speed you wish to go - there is a formula for that as well
but first of all; you need several known factors
output shaft rpm of the motor, weight of the boat (in this case its going to be a displacement weight) and we need to calculate the block co-efficient
For a semi displacement hull, the block co-efficient should fall between 0.4 - 0.45
For a displacement hull, the block co-efficient should be between 0.45 - 0.55
K = speed in knots
Bhp = brake horse power at the propeller
K x √bhp
displacement in tons
This should give you some idea of the formula which you require
Aye
john