While I love the idea of authentic, cast propellers for the Richardson/Southampton RC tugboat, I simply cannot justify spending the $60+ S&H to get a pair of PropShop KNP1720/4's at this point in life. They make a beautiful product, but I needed a cheaper unit to play with, so I found a design (DollarBaySOAR) and I was able to tweak it to suit my needs.

This design will require you to print with supports, and I found that 0.1mm layers made for a prettier print than when I used 0.2mm layers. After printing you'll need to drill a set screw hole in each print, and install a set screw. Finally, you'll need to have your rudders turned fully to one side or the other in order to fit the props between the rudder and the kort nozzle. It's a tight fit, but I have done it multiple times during my sea trials.

I am running these props with the stock gearbox and motors and two Mtroniks TIO 15-amp Brushed ESC's. I get beautiful proportional thrust ahead and astern, drawing just over two amps with both motors at full throttle in a bathtub bollard-pull test. See it in all of it's bathtub glory at:

http://dannyblanchard.blogspot.com/2016/09/rc-tugboat-modifications-deck-winch.html

Feel free to ask questions, and I'll do my best to get back to you in a timely fashion.