A propulsion unit comprising: a shaft being sealed and supported on radial and axial oil lubricated roller bearings (32, 33), said shaft having an axial centre line, a propeller being supported on the shaft via the oil lubricated roller bearings (32, 33), an annular housing being fixedly supported to a support structure, the upper part of which is adapted to be rotatably attached to a hull of a vessel, the annular housing forming a duct for water flowing through the interior of the annular housing, said axial centre line of the shaft also forming an axial centre line of the annular housing, the annular housing surrounding an outer perimeter of the propeller, a rim drive electric motor comprising a rotor rim and a stator, said rotor rim being provided on the outer perimeter of the propeller and rotating with the propeller, said stator being provided within the annular housing and surrounding the rotor rim, characterised in that the support structure is formed of a casing comprising an upper portion and a lower portion, the casing being adapted to be rotatably supported from the upper portion at the hull of the vessel, the shaft is rotatably supported with the radial and axial oil lubricated roller bearings (32, 33) within the lower portion of the casing so that an outer end of the shaft protrudes from a first end of the lower portion of the casing, the outer end of the shaft being sealed with a sealing to the first end of the lower portion of the housing in order to prevent water from penetrating into the housing, the propeller is attached to the outer end of the shaft outside the first end of the lower portion of the casing, said propeller rotating with the shaft, the propeller is a pulling propeller, a first radial plane passing through an axial middle point of the rotor rim is situated outside the first end of the lower portion of the casing and a second radial plane passing through an axial middle point between the bearings (32, 33) being at an axial distance from each other. a shaft being sealed and supported on radial and axial oil lubricated roller bearings (32, 33), said shaft having an axial centre line, a propeller being supported on the shaft via the oil lubricated roller bearings (32, 33), an annular housing being fixedly supported to a support structure, the upper part of which is adapted to be rotatably attached to a hull of a vessel, the annular housing forming a duct for water flowing through the interior of the annular housing, said axial centre line of the shaft also forming an axial centre line of the annular housing, the annular housing surrounding an outer perimeter of the propeller, a rim drive electric motor comprising a rotor rim and a stator, said rotor rim being provided on the outer perimeter of the propeller and rotating with the propeller, said stator being provided within the annular housing and surrounding the rotor rim, characterised in that the support structure is formed of a casing comprising an upper portion and a lower portion, the casing being adapted to be rotatably supported from the upper portion at the hull of the vessel, the shaft is rotatably supported with the radial and axial oil lubricated roller bearings (32, 33) within the lower portion of the casing so that an outer end of the shaft protrudes from a first end of the lower portion of the casing, the outer end of the shaft being sealed with a sealing to the first end of the lower portion of the housing in order to prevent water from penetrating into the housing, the propeller is attached to the outer end of the shaft outside the first end of the lower portion of the casing, said propeller rotating with the shaft, the propeller is a pulling propeller, a first radial plane passing through an axial middle point of the rotor rim is situated outside the first end of the lower portion of the casing and a second radial plane passing through an axial middle point between the bearings (32, 33) being at an axial distance from each other.