A marine propulsion system comprising: a strut having a strut through bore extending through; an inner propeller shaft supporting a first propeller adjacent a trailing end thereof, and the inner propeller shaft having an interface, at a leading end thereof, to facilitate connection with a drive shaft for receiving torque therefrom and supplying a first portion of the torque to the first propeller as well as for transferring thrust, generated by the first propeller , along the inner propeller shaft back to the drive shaft ; an outer propeller shaft supporting a second propeller adjacent a trailing end thereof, and the outer propeller shaft surrounding a portion of the inner propeller shaft ; characterized in that , the inner and the outer propeller shafts both extending through the strut through bore ; a differential gear set being accommodated within the strut and surrounding both the outer and inner propeller shafts , the differential gear set comprising a differential input shaft, a differential output shaft and first and second idle gears , and the differential input shaft being drivingly connected to the inner propeller shaft in order to receive a second portion of the torque supplied thereto and the differential gear set reversing the second portion of the torque so that the differential output shaft drives the outer propeller shaft so as to rotate the second propeller in an opposite rotational direction than the first propeller ; and a leading end of the outer propeller shaft being connected to a leading end of the inner propeller shaft to facilitate, during operation, both rotation of the outer propeller shaft with respect to the inner propeller shaft as well as transfer of thrust, generated by the second propeller , to the inner propeller shaft and back to the drive shaft . a strut having a strut through bore extending through; an inner propeller shaft supporting a first propeller adjacent a trailing end thereof, and the inner propeller shaft having an interface, at a leading end thereof, to facilitate connection with a drive shaft for receiving torque therefrom and supplying a first portion of the torque to the first propeller as well as for transferring thrust, generated by the first propeller , along the inner propeller shaft back to the drive shaft ; an outer propeller shaft supporting a second propeller adjacent a trailing end thereof, and the outer propeller shaft surrounding a portion of the inner propeller shaft ; characterized in that , the inner and the outer propeller shafts both extending through the strut through bore ; a differential gear set being accommodated within the strut and surrounding both the outer and inner propeller shafts , the differential gear set comprising a differential input shaft, a differential output shaft and first and second idle gears , and the differential input shaft being drivingly connected to the inner propeller shaft in order to receive a second portion of the torque supplied thereto and the differential gear set reversing the second portion of the torque so that the differential output shaft drives the outer propeller shaft so as to rotate the second propeller in an opposite rotational direction than the first propeller ; and a leading end of the outer propeller shaft being connected to a leading end of the inner propeller shaft to facilitate, during operation, both rotation of the outer propeller shaft with respect to the inner propeller shaft as well as transfer of thrust, generated by the second propeller , to the inner propeller shaft and back to the drive shaft . <EOS>