Accurate evaluation of the performance of propellers driven by an outboard motor at sea or lake is very difficult due to complicated environmental conditions. In this paper, the hydrodynamic characteristics of two kinds of propellers were measured not only in a towing tank but also in a cavitation tunnel. These propellers have the same geometrical shape except for blade contour and skew line. One of them is used for a high speed motor boat and has a conventional skew line. The other has a cleaver type of blade contour, which is employed for a racing boat.The tests in two experimental facilities demonstrated that under super-cavitating conditions, the efficiency of the former propeller was higher than that of the latter, while the latter propeller was superior to the former regarding air-drawing. These model tests provide us invaluable information to design high speed motor boat propellers.