It has been getting harder shifting from neutral to foward and reverse. More so going to reverse. I was wondering if it could be the cable, the thottle control, both or neither. Any advice would be greatly appreciated.
You could try disconnecting the cable linkage and see if it works good with the controller. My guess is that it is the cable. Try it without the engine running and see if it is better/same.
What year? Was cable ever replaced? What about yearly maintenance? What has been done in the past? Gimball bearing, bellows shift boot and cable. Etc.
It really sounds like the lower shift cable from the manifold to the drive.
Disconnect front shift cable at manifold, and try working the rear manually from the manifold. This will tell you which cable needs replaced.