The propeller fills a unique position in a boat in that it can be used to adjust several
characteristics of the boat. To compare a boat to a car, the prop would be your
transmission, wheels, gear ratio, and tires. Quite a bit depends upon having the right
prop, but finding the best prop for your boat is something of an art.
There are several different types of propellers for models, just as there are for full-size
boats. Almost all racing props are surface-piercers, and run about half in the water and
half out. Running in this manner solves several problems when compared to fully
submerged props, enough so that even some new merchant vessels are being designed to
use surface props.
Octura makes several different classes of props to fit the different needs. The all-digit
props (1435, 1932, etc.) are designed to provide lift and are therefore suitable only in
hydros, while the X, Y, and P series props are multi-purpose props designed to be more
efficient and provide minimal lift but maximum thrust.
On scale hydros, I have found that the X- and Y-series props give better performance
than others. These props provide excellent thrust while angled relative to the direction of
travel, and that makes them equally suitable for both solid and flexible driveshafts.
Because of their higher efficiency compared to lifting props, they provide the competitive
edge a racer needs.
Lifting props do not work well when there is much of an angle to the prop shaft, so they
are far more limited in their applications. There are some boats which just won’t run
without one (usually riggers), so you should have one or two in your prop box. As we
will see later, there are certain reasons to choose one particular type over another.