Re: How fast?
All depends on your set up. If your set up is really bad you will have trouble making it plane out. If it is good then you should be expecting 40 + MPH
My set up in my signature pulls 47 mph (GPS) with 4 adults aboard, however it still pulls the same speed with just me and minimum gear.
Let us all know how you make out and experiment with the set up (trim, loading, motor height etc) till you find the optimum performance.