For what it's worth, my advice to a newbie is to follow the recommendations of the kit manufacturer. With all due respect to both Shipmate60 and Oldiron, it might not be the optimum motor for the model and it might cost a bit more than a "scrapyard special" but at least it removes one potential source of disaster.
Once you have got a "feel" of the model you can experiment a bit with different props, voltages and motors to make it do exactly what you require e.g towing loads, steering tight courses or just sailing sedately around the lake.
Suit yourself.
FLJ