Propulsion unit (11) for propulsion and maneuvering of a maritime vessel, which includes a nozzle (12) wherein a propeller section (13, 13a) is arranged, which propeller section (13, 13a) is electrically or hydraulically driven, which propulsion unit (11) includes a fastening device (16) arranged for arrangement to hull of the vessel or to a steering device arranged for steering and/or moving the propulsion unit (11). The fastening se device (16) is formed by two stems (17a-b) extending in parallel or laterally reversed about an vertical central axis from an upper surface of the nozzle (12) of the propulsion unit, which stems (17a-b) end in a fixing flange (18) for thereby providing an opening (19) which provides the propulsion unit (11) with improved hydrodynamic performance.