the rating of your overflow is an upper limit, not how much you're flowing currently. That depends on the head (distance from your sump's water level to that in the tank, measured vertically, plus some corrections for every bend in the pipe). Measure the head and figure out what your pump is supposed to put out at that pressure.
54g all-glass bowfront corner planted FW
Red tiger lilly, Rotala Indica, Sagittaria Subulata, Micro Sword, Cardinal Plant
Fluorite Black sand and gravel