I recently replaced one of my lower shift cables because it was very difficult to shift and the interrupt switch was causing the engine to die. I put in a new cable and it would shift easily when the outdrive was almost all the way in, but when we tightened down the bolts, it took a lot of force to shift again. After taking a closer look we found that the shift shaft on the outdrive was slightly bent. A few taps of a hammer and everything slid perfectly.