I assume the same is true at rest, no? If not, disregard this post.
Disconnect the cable from the steering bracket at the motor, and turn the OB by hand.
If it's the motor, the grease has congealed in the steering tube (the part the motor pivots on.) Forcing a *lot* of grease in may help, as may judicious application of heat (don't get carried away; there's rubber seals in there.)
If it's the cables, well, you can try to solvent clean and lube them up, but you may be better off going straight for replacement(s.)
If it's hydraulic, then I would suspect the steering tube on the motor.