The marine propulsion set (1, 1′, 1″) comprises: at least one pod (2) that is mechanically connected to a support strut (3, 3′, 3″); a propeller (4) that is situated at the aft end of the pod and that has at least two blades (14); and an arrangement of at least three flow-directing fins (50 to 55, 3′A) that are fastened to the pod (2). This arrangement of fins forms a ring (5) that is substantially perpendicular to the longitudinal axis (X) of the pod (2), said ring lying within a zone (Zx) that is situated between the central portion of said support strut (3, 3′, 3″) and the propeller. The propulsion set further comprises a nozzle (6) that surrounds, at least in part, the propeller (4) and said ring (5). Each of said blades (14) presents an end with an edge (7) coming flush with the inside wall of the nozzle (6) so that the propeller (4) constitutes the rotor of a screw pump.