You don't indicate the brand but on my 86 28.5 I had a Merriman so it's likely that is what you have. Under the steering shaft, on the aft side, about halfway between the cockpit floor and the shaft you'll find a large screw head. That is what holds and tensions the bracket that keeps the cables in place. Check and see if it is there ? If not, the bracket is probably lying on the cockpit floor inside the pedestal ! Remove the compass and check with a flashlight. Then you'll need to find a way to retrieve it and re-install with a new machine screw (not sure but I believe it is 1/4 X 20). If the screw head is not missing, then it could be so loose that one or both cables could have gotten loose. Again you have to remove the compass to try and wiggle the cables in place before putting some tension back on the screw. And if you can't find the bracket at all, here is a model of one you can make out of a small aluminum block. Plus I'm also attaching 2 pieces of info I had save from Merriman. Not related to the cable issue but could be useful.