2001 Mercury 115 salt water control cables?

Hello, I have a 2001 Mercury 115 salt water on a 2000 war eagle center console that I just got used. Its my first real boat. I have a problem, when I give it throttle I'm about 90% through the lever travel before it really starts to throttle up so its hard to drive it between just putting along and full throttle since all that range happens in just the last 10% of throttle lever travel. Not sure if I described that well enough. I have a manual and the cables seem to be adjusted properly at the engine side. I haven't taken the control box apart to see if there is adjustment in there. I'm assuming the cables have stretched. Could anyone tell me how to identify which cables I would need if I wanted to replace them? I believe the control box and cables are original to the 2001 engine. Any advice appreciated, thanks!