You might be able to get improvement with the steering luber. The basic idea is to use a stick  of galvanize pipe with fittings on one end to attach to your cable. On the other end you need a fitting that will allow an air chuck to be attached.
     If it was mine I would try to attach the tool to the cable end at the front that hooks up to the steering wheel. Remove the other end from the outboard and let it point down or away from the boat.Remove air chuck. Pour in  a bit of solvent. Reinstall the air chuck. Attach an air hose with a hand valve. Have a friend attempt to work the cable on the other end back and forth a little bit as you put some air pressure to it, thereby pressurizing the solvent into the cable housing a bit. Make sure your friend holds the cable end pointed away from his body and he should clamp some vice grips on the cable itself to  push and pull with while  putting a little bit of distance between the hand and the cable. Make sure to wear gloves. 
     If you can hook it up this way you won't have to blow solvent and oily debris all over the drivers floor space.
     If you can get some solvent to pressurize through the cable length then it might clean up. After this process you will need to lubricate the cable periodically to maintain the life of the cable. This process does not always work.  If you can put a fitting on the end that came off the motor and then install a plug or cap you can apply some air pressure  and then leave it pressurized for a couple hours. Sometimes this added soaking will break loose foreign material in the cable housing. If it cleans out and you can relube it then you will have saved some money. By this time you can also probably replace the cable if that is required and you need to do it yourself to save money.
     I've replaced a couple and I've also paid to have them done. Not a lot of fun either way. We did a buddies boat 3 yrs ago with this type of system and he saved about $600. Some of those cables are kind of pricey and some aren't too bad.

Good luck, and if you need to see a pic of this contraption I might be able to dig one up somewhere.