I replied to this but don't know what happened to my reply, it dissapeared.
Anyway I have the Profisherman. I put a 19 turn quad and a 7 cell nimh battery with out changing the esc and got good results. It is very fast. But remember this boat is not designed to go that fast. Too much speed and I don't think it will stay together. It will deffinetly become unstable.
I think the upgrade I have done is about the most you can do to that boat with good results. I would say the top speed with good handling on this boat is about 21 to 24 mph tops.
If you want something faster then check out some other boats.