Does Tuhorse 3" pump fit 3" deep well?

Yes. Tuhorse 3" pumps fit 3" casing, but it is a tight fit. 3" well casing actually has 3.068" I.D. (by regulation code), and the pump is 2.95" including the cable guard and the screws on the pump body.

You may ask how the water can get into the suction port located near the center of the pump with the small gap around the motor.  The answer is that the motor and the pump-end is 2.75" excluding the cable guard, this gap between the motor and well casing is sufficient for the water flowing along the motor surface into the port, and in the meantime to cool the motor. 

Please note that these days some people drill their shallow wells by themselves using regular plumbing PVC pipe for well casing that has smaller than 3" I.D. This 3” pump will not fit in those pipe.   Please use real well casing or have a licensed driller to drill your well.

http://www.tuhorse.us/categories/submersible-pumps/3-inch-deep-well-pumps.html