Aftermarket may or may not have the same output, it can also come full of metal grit, and they should be tested by hand to turn with relatively low resistance, so the worm gear doesn't get destroyed, but I even check OEM ones for resistance because I've seen some lock and strip the gear.
And try to determine why it stopped working. I have an Echo 355t I just found a stripped oil pump gear on, but in this case the pump has the plastic gear, and the worm gear is metal, and the pump is not serviceable, can only buy a whole new pump. The resistance doesn't seem too much in the. Pump, but I'll never know.