Chris,

There may not be a prop which gives you 4,500 rpm. My guess is that if you go one step lower in pitch, you will get a bit more than 4,500 at full throttle. That”s just a guess, and the only real way to find out is to keep trying different props until you find the right one.

Keep in mind that factors other than the prop will affect max rpm. The bottom of the boat and outdrive should be clean, the engine should be tuned, and the load carried should be average. Also, unless you like racing, the prop which produces the max rated rpm from the engine is not necessarily the best prop. I have found that “overpropping” a boat a bit can increase fuel efficiency, so you may already have the best prop from that standpoint.

Before checking a lower pitch prop, measure the fuel burn per hour with this one. If you do not have a fuel flow meter, you can do that by just filling up the boat and running at cruise speed for a set length of time, then filling it again. By the time you’re done, you will have slightly used props on your hands. Keep one as a spare and sell the rest on eBay!