"Depends on the motor size and
"Depends on the motor size and some other factors as well. I have the AQ125B and i currently have a 14x15 installed on my 86' 18.5ft bayliner. It works well for pulling skiers. Max speed is about 34mph (est.) with four adults on board. If you are looking for higher speeds, you may want to go with a 14x17 or 14x19. Beware tho, the boat may overheat as the prop is spinning too fast without the proper friction. If you are looking for pulling power, the 14x15 is a good choice, or you may look at a 15x15. HTH, and I hope I didn't confuse or lead you down the wrong path.....I am sure El Pascador will correct me if I am wrong. (PLEASE DO IF I AM WRONG!)"