To get the power to the prop, use one of our stainless Drive Dogs. Accurately bored hole accepts shafts without ANY "slop", precision "ears" fits all standard props. Single setscrew provides plenty of grab with a single flat filed on the shaft. Unlike two set screw drive dogs known to split and weaken the shaft. Small O.D.'s perfectly concentric matches outside prop hub diameters respective to their size. BEWARE of loose fitting, poorly machined drive dogs using inferior cheap stainless! Ours are guaranteed accurate or your money back! Comes in 1/4" (.250) and 3/16"(.187) sizes.