Aftermarket gear set quality is not the problem you face. To set that up correctly will require special tools in order to set the pinion to the proper height before backlash will be of importance. Otherwise, the gears will either be contacting on the heel or toe of the teeth. Your best bet would be to find a good used lower. If you want to have that one repaired, I would suggest locating an OMC tech with 20 or more years experience.