It could be the control itself (less likely), the engine linkage (more about that later) or the cables themselves (most likely).
You did not specify if the issue is with the throttle or the shift function or both. To check, use the gear disengage button on the control so that you only move the throttle cable at the motor. If that is not tight, the problem is probably not that throttle cable, the linkage or the helm control.
Now with the motor not running, try carefully to move the engine control into gear. One direction may be locked out so don't force it. One direction, forward or reverse will most likely move. See how hard that is. If it is hard, it may be the cable or the shift mechanism at the motor (or the LU itself, low probability but possible). If tight and binding, disconnect the shift cable at the engine and see how the cable moves. If still tight, the cable is probably shot. If not tight, try moving the shift lever arm by hand or with a pliers to se if the gear box is binding.
One other simple check is to take a look at the cables near the motor for bumps or obvious corrosion. Bumps mean the the cable is corroded and the rust has swelled causing the bump. In that case, cables need to be replaced.
