A chopper is a

propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

design largely of interest for production outboards on fast pad v-bottom boats. Unlike a cleaver the chopper's trailing edge extends aft with a large chord line at each radius. Choppers provide good acceleration and top speed and generally have relatively high rake, which has the effect of increasing the boat's angle of attack without changing the motor trim. This trimming effect is mistakenly called 'bow lift'.

External links

Racing Propellers by Mercury
Propellers {{Shipbuilding-stub