HORIZONTAL PROPELLER THRUST A CASE WHEN EQUAL POWER DOES NOT NECESSARILY MEAN EQUAL SPEED.  
There is a hidden advantage in the design of the 47LRC SEries model's engine placement. It has a perfectly horizontal engine and propeller shaft. It's an advantage because the thrust is what drives the hull through the water. Any vertical component of thrust is simply wasted energy. Therefore, the more horizontal it is, the more efficient it becomes.  
Horizontal Propeller Thrust 

FASTER 

With the exact same diesel power engine, the horizontal component of engine thrust A is greater than because there is no wasted vertical energy component.  
SLOWER 

Since power is not directed in a horizontal direction, there is wasted energy in the vertical direction. Therefore, forward thrust B is less than A above. More fuel is burned to match hull speeds. 