The influences of variation of number of blades and pitch distribution on characteristics of screw propellers in open water are studied applying the theoretical method of the previous papers (Journal of the Society of Naval Architects of Japan, No. 100 & 101). The propeller efficiency grows higher with the number of blades if the blade area ratio, pitch ratio and drag coefficient are constant. The effects of variation of pitch distribution on the efficiency are very small for moderate slip ratios (0.20.5).