Use of Bp~Delta diagram for prop selection

[pavel915]

I am learning to use the Bp~Delta diagram for propeller selection.
The process i go through is:
at first i assume a suitable and reasonable value of rpm and shaft power.
then according to calculated Bp ; using the optimum efficiency line i find the value of delta and p/d and from the value of delta i can find the diameter.

But if the found open water efficiency doesnot give my required effective power then i run along the fixed delta curve(with delta value previously found) changing the rpm (power is constant) and i find new values of diameters.
then i plot a Diameter vs Effective power curve and select the diameter gives my desired effective power.

I dont have good books on propeller selection. So want to know how much right my process is and what additional things should i do to select the propeller.

thanks in advance