Are you testing the thrust on the bench?
Testing thrust on the oversquare props like 7x10, 7x13 or 8x23 won't give a very good idea of how they'll perform in flight.
These props will give you horrible static thrust results below 100mph airspeed, but start producing big thrust once they're moving forward and the relative angle of attack to the blades starts decreasing.
You could blow a leaf blower on your test rig and THEN measure static thrust!!