How were the conditions when you made these passes? As I mentioned above, I'm sure the numbers on the GW website are in perfect or ideal conditions and with very little fuel or extra weight on board. Your boat per the GW website says that you have an 80 gallon fuel tank, of which a gallon of gasoline weighs around 6 lbs per gallon, which would be approximately 480 lbs. If they did the tests for the website with only say 10 gallons of fuel on the test boat then that would only be about 60 lbs comparatively, or about 420 lbs less. At which point, I wouldn't be surprised to see them get higher rpm as well as mph numbers. I'd do a comparison, next time you're running low on fuel and have say only 10-20 gallons of fuel on board, then take the boat for a test drive and see what kind of max performance numbers you're getting, as well as maybe empty out the 10 gallons of water. As a gallon of fresh water weighs 8.33 lbs per gallon, which will add 83.3 lbs to the equation as well.