It is more likely that your prop has too much pitch. (tires are way to big) Your kv is only good up to 24,420 RPM, you want to be closer to 30,000 RPM.
3s would be the most you would want to run, that takes it up to 36,630 RPM and will give you a huge boost in performance. You need a proper prop though!!!
A proper setup boat will also run much faster then poorly set up one. Your first step is to make sure you are running the right prop.