If the steering is still stiff it's going to be 1 of 2 problems. Either the steering cable is worn out, and binding internally, or there is corrosion in the pivot tube that the steering cables go through. You have 2 choices as to how you want to approach this. (I understand that time is money, but I do not know which one is more valuable to you).
Choice 1 is to pull the boat form the water, remove the outboard, disconnect the steering cable, pull the cable out of the pivot tube. Clean the inside of the pivot tube with a cordless drill and a 10 gauge shotgun barrel cleaning brush. Grease the cable end, put it all back together, put the boat in the water and see what happens.
Choice 2 is to do all of the above, but replace the cable and helm unit at the same time (the helm is the steering box behind the wheel).
Steering cables are a wear and tear item. Over time they get grooves worn into their inner jackets, and the steel cable core gets pulled into those grooves, causing a bind and tight steering. The cables life expectancy is 12 to 15 years. If you are on the original cable you might just want to replace it first. If you are not sure, and want to try taking it apart first, the cables and helm kits run about 160 to 180 bucks depending on the length that you need. Does that all make sense to you?