On most outboards the zerks on the tilt just lube the tilt shaft.
Dangerous, but I have used this technique many times. Get a concrete type nail gun, the type that uses special .22 blank cartridges, get face and eye protection plus heavy gloves, then with NO NAILS IN THE GUN, place the end of the gun on the end of the steering shaft, BAM, The sudden shock has always freed them up for me. BE CAREFUL!
Now pull the shaft out and clean it and run a big bore cleaning brush and swab through the bore, ( I use one from my muzzle loaders). No go to West Marine and buy a new nut for the end with the zerk fitting and repace the old nut. Give this a shot of good waterproof grease regularly while some one is turning the steering wheel. I use "Corrosion Block" brand grease.
Be careful!
Now a few words for the stupid alpha hotels who call themselves engineers and design a stainless steel shaft to operate a critical steering system through an aluminum housing while soaking in salt water:moon
Tom