Have you serviced the existing motor? I'm guessing there are videos on how to along with other threads on this forum.
I take them apart, remove the residue from the windings and inside the motor, wash it down with CRC QD electronic cleaner, relube, etc. Disclaimer: I've not watched a video on it nor researched in this forum, so I could be doing it incorrectly, but the motors seem to run stronger when I'm through.