~1700kv for 6s sounds good, geared for around 35-40mph it should run fine.
Unlikely as it is, there may actually be something wrong with your current neu motor- have you tried it in a different vehicle at all to see how the temps do?
Ok then the tekin or the mega will be a good chose?
I ran the neu 1515 3d on a kyosho kanai and the motor run a few coler about 165f I have a eagletree graph on the kyosho kanai. the most watts that it do was 1600wats and 68amps