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