Now my build is working well and because by following all you comment help me a lot I want to share few details with you. May be it can give you some ideas or help you.
I began with same motor and reduction of @pacificmeister. After I follow My own way!
Propeller: solas 71/4 x 6
Batterie 8s 20ah but place to have 12s and 40ah
Max speed 23 kmh
Remote and reciever: home made