The author who stated the outline of the theory of free-running screw propellers in his previous paper (the Journal of the Society of Naval Architects of Japan.No. 100, p. 15) calculated the characteristics of the practical propellers and proved that the theoretical values agree nearly with the experimental results, and suggested a method of design of optimum propellers. Finally the following results were obtained : 1. The characteristics of 3- and 4-bladed propellers are mainly due to the breadth and contour of blades, and the cascade effects are negligible. 2. Skews of ordinary type propellers have little influences on the characteristics. 3. Weissinger's method on the single wing is applicable to calculate the characteristics of screw propellers. 4. The values of k ₁ (ξ') can be calculated by the author's method, but can not be forecasted immediately. If this values are initially known, the characteristics of propellers can be calculated very simply and very easily by the strip method. 5. Modern propellers analogizing from one of B₃-50 type (Transportation Technical Research Institute, Japan) have nearly an optimum efficiency in open water.