Re: 1976 merc 850 question.
Hi, ed, you'll notice where the shift and throttle cable come in on the Port side of the engine, right on the inside of the motor cowling there's a black, oval-shaped insert with 2 round holes into which the adjustable ferrules on the shift and throttle cable fit. There is a locking clamp assy that flips down and latches over both of the cables to secure them. To release, you'll see a little "tee" lever at the top of that latch. Just kinda push inwards at the bottom of the latch where it hooks into the control cable mounting bracket and the latch pulls upwards to release.
At the end of the throttle cable you'll undo the nut holding it to the throttle arm. Once the throttle cable is lifted up you can see the spring-loaded fixture that secures the end of the shift cable. All you do there is loosen the nut with a 7/16" socket (don't take the nut all the way off). Then, the shift cable fixture lifts up and pivots sideways to release the shift cable.
After that, just work the cables thru the rubber pieces at the front of the motor and you're free! Throttle cable goes out first, then the shift cable.
Note, when you go to reinstall the cables, the shift cable goes in first, the throttle cable last. The easiest way to tell which is which, if you don't mark them, is to flip up the fast idle lever; whatever cable moves is the throttle cable.
HTH..........ed