Re: simple question
IF -- and I say IF the two props are from the same manufacturer and same series (model) THEN you may see the rpm change 150 - 200 rpm/inch of pitch (up or down). If the props are not from the same manufacturer & series, one is cupped the other not, then all bets are off. Speaking from about 7 years experience using props from 13 - 19 (stainless and aluminim, cupped and uncupped) on that same identical motor on a 16 foot aluminum walleye boat, I always came back to the 12-1/4 x 15 cupped aluminum. It put the engine at 5800 RPM with two aboard (my average load) and popped the boat on plane quickly. Regardless of load a 13P just dug a hole. 17P uncupped performed very nearly the same as a 15 cupped. 19 was too much bite. The slight difference in diameter is a function of design and not a major consideration. That was two boats ago so exact numbers (except the 12-1/4 x 15) are becoming lost in the cobwebs of this aging mind. All of the props were sold long ago.
