carla - Those prop calcs are pretty accurate . . . and a great way to tweak your setup. This is my favorite online calc.
http://www.go-fast.com/Prop_Slip_Calculator.htm
Just wait until you play around with a bunch of 17 Pitch props . . . I compared a bunch of new 17Pitch props and there was nearly 1000rpm difference b/w the highfive and rapture.