Re: 1989 Starcraft Islander Steering
Welcome aboard, MEhunter. Several things could be causing your steering woes. As you asked, the cable along with the steering box behind the dash or the steering spindle in the outdrive (we are talking I/O, right?). Disconnect the cable at the drive end and turn the wheel. If it's still hard to turn most likely cable or box. I would just get a new rotary steering system which includes box, cable and in some cases, steering wheel. Here
EZ's source for an affordable system. If it is getting stiff, any fix is a band-aid. While the cable is still off grease the outdrive and check that it swings side to side easily.
Also, pics, lotsa pics. Pics keep the Mob happy. Again welcome aboard and have fun.