Question for the Gurus here

[Cam]

Lately when I shift into gear (forward or reverse), I am getting grinding, as it takes the throttle arm almost full throttle to engage. I have noticed though, that if I shut off the engine and work the throttle back and forth from forward to reverse a few times, this symptom goes away. The motor is a Johnson 150 Oceanrunner, 1996 model. Is this the shifting cable or something in the gear case? Either way, how do I fix this problem? Thanks in advance.