The TugBoat has always been the work horse of the fleet. One thing that has always been tough is to get one that is the right scale.
I offer a true Navy Natick Class YTB tug kit to you. This is a .03 thickness hull, pilot house, structure, and funnel, all printed in one kit. Even the rudder is included with a predrilled hole for the shaft and stuffing box.
I used a 2mm shaft and stuffing tube and Prop from Model Boat Bits in the UK:
I also used a servo for propullsion rather than a speed controller and motor to save on weight. With my model, I had to add 2 1/2 oz of weight to the stern to get it down to the waterline.