I agree totally with Tica.
This is a sailing yacht, which would use the engine for moving about while in harbour but most time it would be under sail. When under power of the motor, it would not be very fast, so keep your model accordingly.
I do not put motors in my sailboats. If you do, you are looking at speed control, bigger battery pack, plus, the motor, stuffing box and so forth.
Will you be sailing your model with sail’s furled and vessel under power? Or, are you planning to sail it under way with full sails ?