How closely did you inspect the worm gear that slips on the shaft that is on the motor itself. You test with a new motor seems to narrow it down to gearing...right? I have seen a very fine split in the worm gear that is not very noticeable and affects engine performance. Do you have a lighted magnifier glass? Hoe hard was it to remove and replace from the old to the new motor shaft?
![[Image: 7071.gif]](https://www.allsmileys.com/files/sweetim-texticons/7071.gif)