This paper presents an investigation of the effect of a non-uniform suction flow on forces on the impeller of a waterjet pump. In such a pump, used for ship propulsion, the non-uniformity of the suction flow is caused by the boundary layer under the hull of the ship and the shape of the inlet duct. The paper covers both experimental and numerical studies. A model of a mixed-flow waterjet pump is built into a closed-loop test rig. In order to measure the instantaneous forces and bending moments on the impeller, a newly designed co-rotating dynamometer is used, which is built between the impeller and the shaft of the pump. The design of the dynamometer will be presented. Various entrance flow distributions to the pump are achieved by means of a device situated in the suction pipe. In this manner the axial velocity at the inlet of the pump is varied between uniform and non-uniform distributions. Results of measurements show the influence of suction flow and blade interaction on forces. Results of experiments are compared with CFD calculations of a waterjet pump installation with similar entrance flow conditions. Quasi-steady calculations are performed for the pump which is equipped with a vaned stator bowl. Calculations show a good quantitative agreement with measurements.