I don't know what the max rpm is. Website says practical range is 1400 - 6000 rpm, so on the ground 5500 is probably about right. No tappets or pushrods, so maybe it could go faster. Switching to a 14x14 would give more speed, but still no more than maybe 80 mph. Does anyone even make a prop like that? Fortunately I'm not really looking for speed.