With all the other maintenance you do on your boat, don't wait until the boat's cable steering begins to tighten up before you lubricate the point where the steering cable interacts with the motor. Salt spray or water will eventually penetrate the steering tilt tube--the steering link arm, where many steering problems begin--and cause rust to begin to accumulate within the tube. A little preventive cleaning and lubrication with the right kind of grease can stop this problem before it starts.
Unbolt the steering tilt tube (the steering link arm) from the outboard motor using a 9/16-inch socket wrench. Remove the steering arm from the tube and sand it with extra fine sandpaper.
Clean any hardened marine grease from the inside of the tube by spraying the inside of the tube with a penetrating lubricant. Thread a piece of extra fine sandpaper into the rod from a firearm bore cleaning kit, attach the rod to a drill and put the tube into a bench vice to hold it tightly. On slow speed, run the cleaning rod through the tube. If the inside of the tube is badly rusted, replace the tube with a stainless steel tilt tube to avoid future problems.
Replace the nut on the tilt tube with a nut that has a zerk fitting (a nippled grease-gun fitting) for future lubrication. Tighten the nut in place.
Grease the cable through the newly installed grease fitting with a grease gun, using the marine grease recommended by the steering system manufacturer.
If your boat has a rack and pinion helm, it's a sealed unit and requires no maintenance. If you have to replace a rusted tilt tube, it's likely that the cable is rusted as well and will require replacement.
This project involves work with power tools and other equipment; appropriate caution is advised