If you disconnect the outboard drag link and the wheel turns easily but the outboard is still hard to turn, then the pivot tube is most likely seized. There are two solutions: either heat the tube and push more grease into the bushing while turning the outboard, or disassemble the pivot tube and clean out the old grease.

In this video I try to free the completely seized steering bracket on a Yamaha 50HP four stroke. It turns out to be beyond repair, but the video still shows taking the mid section apart to get at it.

A repair that worked, freeing up a seized pivot tube.