I think you are on the right track. You will find the boat responds a lot better with a 17. Your hole shot....punching out from a dead stop, will be improved....faster response and more solid. If you like to cruise just above planing speed, you will be able to maintain your set mph better and reduce the tendency to fall back off plane requiring a throttle advance, which gets the boat back on plane which then runs away with you and you have to cut back to where you wanted to run and etc. Last it will get your rpms up where they belong which will help to preserve your equipment and higher rpm throttle advances will be more responsive. Depending on what changes as a result of reducing the pitch, you may not loose any top end or if you do, not much.
To keep things where you expect them to fall, get the part number off your prop and somewhere in the number will probably be the numbers 19. That is probably the pitch and you will be wanting a prop with the exact numbers except change the 9 to 7. Otherwise look up the number which will put you in a type/style/function....etc of a series and just move up to the previous prop which normally would be 2" less pitch.
Stay in touch.
Mark