Your boat speed is directly related to your rope length. If you use a longer rope, you need a faster boat speed, so you don't get slack in the line. A shorter rope requires slower boat speed, because otherwise there will be no wake to jump. For beginners I suggest 15-18 miles an hour. This speed is only for when you just start off, once you are stable right around 20 m.p.h is good. Most pro wakeboarders go about 22 m.p.h. Personally, I use a about a 47' foot rope and go about 22-24 m.p.h., depending the type of boat I'm riding behind. Remember that if you have a ski pylon inside the boat you have to add that length.