sounds like a simple issue from using grease that "sets" - simple fix is a sharp tap on the end of the steering rod with a lump of wood - don't hit it hard enough to bend anything - just have to break the "set" grease and it should be free as a bird after a few cycles back and forth from lock to lock.,
bought a boat a few years back that had this issue and knocked the price way down cause of the stuck steering - was pretty confident looking at the motor (no obvious bend) and given the owners story - haven't used it in 9 months - can't see why it would be like that (and using a bit of judgement as to the bloke's character) - 1 softish hit with a bit of wood once had the boat home and steering was all good - for a few years till we sold it to upgrade.