Shah. I think you need to speak to a shop that sells fast boats/racing boats/offshore types, Prestwich model boats, for instance;
There are too many factors to be considered for a powerboat such as you are contemplating…. Hull form, Prop location (sub-surface or surface drive, type of drive..battery selection (voltage and type) and so on to even guess what motor you should be looking at, at this stage; and do you want to just go fast or actually race?? if its racing you are going for, a club is a must fir this aspect of model boats.
There must be powerboat forums out there, they would likely be a better bet for this, it is a bit specialised.
If this is your first boat, it may be advisable to start slightly smaller and get the hang of the gear and indeed the controlling of a boat at high speed.
Ashley