Motor
HI and welcome to the site
Sounds like a nice scale model and at that size should look very realistic on the water.
Given your criteria and the size of the prop you will need a fairly substantial motor and possibly a reduction unit (2:1) between the motor and prop to reduce the load on the motor.
many years ago (at New Brighton on the Wirral) we used to have model tugs with similar dimensions and prop size and were able to use ex computer motors supplied by one Bert Alt 👍 . Sadly such motors are no longer available so you will need to source a more readily available motor.
As you want tork rather than speed a brushed motor will suit your requirements. I have friends who sail similar sized and propped fishing boats and they use Graupner 700/800 sized motors or the Buhler equivalents. The latter are often used in electric showers and can be found on line from model suppliers and the secondhand market.
Your 7.2 volt batteries will work fine with 6volt motors but may somewhat underpower a 12v motor. You could use two in series (but check the max volt of any ESC before trying this) or buy a 12v NiMh. However if you have all the power and speed from 7.2 volt this may not be a problem.
I suggest you find and join a local boat club, if you haven't already, as you will then have the benefit of their knowledge experience in fitting and selecting a suitable motor.
Good luck and please let us know how you progress or need any further help. 😀
Live long and prosper
Dave
