For decades, feathering propellers have operated as a result of the water flowing over the blades, combined with some friction of the shaft and/or transmission.
In recent years radical changes in sailboat engine transmissions have created new issues for propeller manufacturers. The advent of hydraulic transmissions as well as the electronic gear shifting.
In both cases, the transmission (whether in gear or not) presents almost zero drag on the shaft when the engine is not running. Some shaft drag is always necessary for a propeller to either fold or feather. However, with these new types of transmissions, there is no drag and the helmsman does not have any mechanical way to slow the shaft down from freewheeling when the engine is stopped.
To that effect, the Max-Prop engineers have invented a patented radial spring which is incorporated inside the body of the Boomerang model. This spring solves the feathering issues by forcing the blades back into a feathered position as soon as no torque is applied to the shaft. Once the engine is either in idle or shut down the blades will feather within seconds, regardless of the shaft rotation or the boat speed at the time.
The Boomerang model has been in testing since 2016 and has already been adopted by many European boat builders.
The Boomerang does not require water flow to feather the propeller. The internal spring brings the propeller to the feathered position. Perfect for use with electronic shift mechanisms and hydraulic transmissions.
A 5 blade Max-Prop Boomerang on a high angle shaft will have substantially less drag than a fixed 2 blade propeller while providing much more power while motoring.
The Max-Prop Boomerang has 96% efficiency of a fixed blade propeller in forward. The torque of the shafts opens the blades immediately to the most efficient pitch in both forward and reverse. Maximizing efficiency under power with five blades to get the vessel moving and keep propeller noise to a minimum.
If your engine achieved too much or too little Rpm at maximum throttle, you can adjust the pitch to a higher or lower setting to attain the correct Rpm. Pitch adjustment can be done in the water as the propeller does not need to be disassembled to change the pitch.
The Max-Prop Boomerang provides 80% more power in reverse than a comparable fixed blade propeller. The Boomerang utilizes the same leading edge in forward as it does in reverse giving the propeller the same efficiency in both directions dramatically improving control and power in reverse.
Due to the design of the Max-Prop Boomerang, installation is a simple bolt on, can be done in or out of the water.