Why is my 17 foot mako steering cable frozen

I've been able to free some frozen cables in cars and bikes (though I haven't had to do a boat steering cable) . Try tilting the cable into a vertical position as much as possible, then running Liquid Wrench down between the sliding cable and the sheath. Then judiciously flex the whole assembly and push and pull on the sliding part. It may take patience over a period of days. Once you get a tiny bit of movement you're close to full success, as long as corrosion hasn't caused some of the strands of the cable to break inside the sheath (failure to move smoothly, once it's moving, might tell you that's happened).

WD-40 would probably work as well, and it is less smelly than Liquid Wrench (to my nose, anyway). Either way, you'll have an oily drippy mess to dry out after you're done, but it may save buying a new cable.

Replace the cable.it is binding inside.

Most of the time the cable is frozen in the tilt tube, the tube it bolts to on the engine. Loosen the 1- 1/8 nut on the starboard (right) side of the engine where the cable enters the tube. If there is a rod extending from the opposite side, put penetrating oil on it and hit it with a heavy hammer to get it moving. If only a short nub is showing, remove the link arm from it and hit it with a punch till it will come out the other side where the large nut was attached. Sometimes the engine needs to be removed from the boat to allow clearance, but can just be suspended behind the boat for this job. After the cable is removed from the engine now try to move it withe the steering wheel. If not moving replace it with new. If it will move now, even if a little stiff, lube it up and work back and forth to free it up more till satisfied. Be sure to clean, sand or file the tube and grease with a good sticky grease before re assembly, tighten all fasteners. Good Luck.