No one can tell you what will be best until you do some testing. There is no 'best prop' because it changes with every weight of every boat and how the boat is created.
Buy a tachometer like a tiny tach, hook it up, then go run the boat with the stock/current prop and tell us the RPM's you are getting. Then find out what the current prop is- what pitch and diameter. Only then can anyone tell you if you are hitting the 'correct' RPM's and/or speed for your setup.