Top Speed??

I have a 1987 v-20 cuddy w/1993 200hp Johnson Ocean Runner. I've had it at 5300rpm with the top down, less than a quarter tank of fuel, calm day and all trimmed out at 45 knots. That's about all I want it to do anyway. My gps displays top speed at 47.7 knts but that is running with the tide. However this year I'll keep a close eye to make sure I stick around 4k rpm's. Fuel in Savannah is over 2.00 on the water and 1.65 at the pump and looks like it'll be going even higher.