Unidirectional torque boosting propeller

A marine vessel comprising:

• a propeller device, said propeller device comprising;
• a main shaft;
• a front propeller provided on the main shaft, the front propeller having a hub and a plurality of blades extending radially outwardly from the hub;
• a rear propeller being co-axially to and spaced apart from the front propeller backwardly in an axial direction, the rear propeller having a hub and a plurality of blades extending radially outwardly from the hub, wherein an adaptor is coaxial with the main shaft, said adaptor comprising a second shaft for supporting the rear propeller and a plurality of pitched-formed seating surfaces having ramps, the pitched-formed seating surfaces being spaced apart from the second shaft in the axial direction, and the adaptor communicating with a rear side of the front propeller in the axial direction;
• and
• a plurality of locking elements resiliently movable in the axial direction, one of said locking elements being in contact with one of said pitched-formed seating surfaces and communicating with the rear propeller.