Duoprop
Duoprop is the name of a boat propulsion system developed by Volvo Penta .
On the shaft of a drive there is a counterclockwise and a clockwise propeller , which rotate in opposite directions when driving. The front propeller (seen in the direction of travel) is supposed to provide the main thrust and is larger than the rear propeller. The rear propeller is smaller and is intended to convert the turbulence of the main propeller into thrust. For this purpose it rotates in opposite directions. The drive requires a special propeller set. These are available in different versions. The 'A' series is designed for diesel engines, whereby the smaller propeller is partially designed with four blades (for diesel engines of the AQAD type with a fixed turbocharger and without a compressor). The 'B' and 'C' series are used for gasoline engines, with the 'B' series made of aluminum and the 'C' series made of steel. Volvo Penta prescribes steel propellers for powers above 400 HP.
The advantages of this drive system over a conventional one are good directional stability, up to 30 percent higher acceleration and up to 5 percent higher top speed, in partial load operation a 10 percent lower consumption, better grip in the water and thus faster planing, a lower one Noise level and no wheel effect and therefore no side drift when reversing.
There is a similar concept from Mercury Marine , where it is called the MerCruiser Bravo III, and from Yamaha , where it is called TRP. Suzuki Marine has been using a "Suzuki Dual Prop System" in its DF350A outboard motor since 2019.