96 mercury 115 control on engine is stiff

[repair man]

have a 96 mercury 115 with og31 serial # the control box is very stiff with the cables disconnected from engine and it seams like the control on the engine is very stiff. according to the owner of the boat it has been this way since bought the boat. the throttle cable is all the way at the end of its adjsutment and has been that way since the boat was rigged. im thinking that it needs a control box and supreme cables even though its on a 19 ft bass boat. my real question is how stiff should the control be on the motor be? its not so much that its stiff its that it takes alot to move it. the spring in the control its self seems like it has alot of tension on it. is that normal? im pretty sure when the boat was rigged at the factory or the dealership they never caught the problem with the control box & cables or it was put together wrong. any help would be appreciated greatly