1990 Yamaha 130hp not going into gear

[GuinnessLaxer]

I have a 130hp Yamaha outboard that will not go into gear all the time. The linkage is working fine and doesn't need to be adjusted. I have moved it from neutral to forward & reverse using the arm near the powerhead and it goes into gear, most of the time. I'm not sure, but this sounds like it might be a lower unit issue.

Does anyone have any thoughts and/or suggestions?
Thanks in advance!