my GTX hit 60 once, but, it was took back out ten mins later and the impeller sheared...
just got it fixed up and goin again, managed to hit 52 on a midly choppy lake rayburn according to the occasionally working speedometer, i think i need to run some carb cleaner through it and buy some new plugs...
I have two identical 97 GSX. Top speed recorded on the digital gauge is 57 on smooth water no wind. Engines have been top end rebuilt and bored to 50 over.