Disclosed is a ship propulsion system comprising a synchronous machine (6) with an especially superconducting rotor winding that is to be subjected to intense cooling and a normally conducting stator winding (11) which is to be cooled. The stator winding (11) is disposed at least in part inside a support structure (14) encompassing a hollow cylindrical magnetically soft outer body (13) and web-type support teeth (21i) that extend in an axial and radial direction. A hollow cylindrical part (15a) of an exterior housing (15) encloses the outer body (13). In order to cool at least some areas of said housing part (15a), the stator winding (11) is thermally coupled to water as a cooling medium (K) via the support structure (14) and the housing part (15a).