I am new to boating I currently have a 2016 Bennington ssrx with a 90 Yamaha. The Max RPM I get is between 4200 and 4300. From what I researched I'm supposed to be between 5500 and 5800 RPMs. The prop I have on the motor is a 13.25 X 17. I have called two different dealers and found the ballpark but 13 and 5/8 X 14 or a 14 X 14. My question to y'all would I increase speed or would this make my boat go slower going down in prop size. FYI max speed for my boat is 20 miles an hour.