Engine O.S 46 MAX has a movement specification of 0,46 inch3 or 7,53 cc with the piston diameter of 0,86 inch or 22 mm and the stroke length of 0,72 inch or 19,6 mm. Engine O.S 46 MAX is able to produce power of 1,63 hp on machine rotations of 13.000 rpm. Engine O.S 46 MAX needs propeller to maximize the work of machine O.S 46 MAX. The propeller’s sizes suggested for engine O.S 46 MAX are “10x4”, “10x6”, “11x6”. To determine the best propeller size needs engine O.S 46 MAX specification test by using several propeller’s sizes to get rpm and torque data resulted from the propeller test of engine O.S 46 MAX and finding out the propeller’s size that is suitable to the machine specification by calculating theoretically.The test to find out the propeller’s size that is suitable to the machine specification is testing the rpm and maximal torque on each propeller’s size and calculating the advance ratio, power, and efficiency resulted from each propeller’s size. The test result shows that propeller with size “11x6” is the best propeller for engine O.S 46 MAX based on the maximal rpm test is 11.011 rpm and maximal torque is 4,66 N.m and the calculation of advance ratio is 1,27, calculation of power is 9,32 hp, and efficiency resulted from the propeller is 89,31%, that reaches the highest score compared to the other propeller’s sizes.