Overheating electric motor after 12 Mille run.
 

My 48 volt motor overheats after a 12 mile continuous run, exceeding 175 degrees. 2011 club car with 10 inch tires, high speed gears, 25 lbs pressure, 2 persons riding , convertible 4 seat configuration. Should this be considered normal?

That is not unusual to reach that temp 175 F after steady run with 2 passengers.
And a 4 pass rear seat let of extra weight.
Of course you did not mention your average speed but I am sure it is 20 or more.
The high speed gears of 8/1 add to the motor temp due to loss of torque.
It would help to run at lower speed for a cool down time after running for a period of 5 miles at high speed.