Abstract: Hub assembly for the journalling of an impeller (4) or drive shaft end (3) in the pump housing (2) of a water jet propulsion unit for propulsion of a vessel. The hub assembly forms a separate, integrated assembly (6) which as a single unit can be assembled and dismounted from the stem without requiring the pump housing, impeller or drive shaft to be removed from the vessel. The hub assembly is joined together by means of a tightening nut (15), screwed onto a sleeve (9), with an inwardly positioned bearing plate (16) axially holding the sleeve in a bearing housing (8) while concurrently clamping the bearings (10, 11) between said bearing plate and a radially extended flange (17), arranged in the front end of the sleeve, so that the bearing housing, the bearings and the sleeve form a separate, integrated unit.