In order to obtain the necessary information for designing the propellers of fishing-boats, the mean wake fractions at the propeller position were measured by the means of blade-wheels on twenty-six models, in which the volume-length ratios, prismatic coefficients and breadth-draughtt ratios are varied systematically within the following range. Volume-length ratio ∇/(L/10)3=7.5_??_15.0 Prismatic coefficient φ=0.55_??_0.75 Breadth-draught ratio B/T=2.2_??_3.0 The range of speed in the experiments covered from 0.20 to 0.38 in Froude's number, and from the results obtained the effects of the above factors of hull forms, speed, trim and vertical position of the propeller center upon the mean wake fractions were studied.