[pelican]

if the steering is stiff now,and it wasn't previous:
you haven't stated if it's a new engine,or used.there's one way to find out the problem -
disconnect the engine from the steering cable - see if the engine moves side to side freely - if it moves freely - sping the helm - is it stiff ? stiff,it's the cable,replace the cable...
if the engine's tight - the bushings on the tiller arm - located at the top and bottom of the clamp/swivel assembly,these,on occasion will become tight - seawater hits these,the water evaporated,leaving the salt behind.the salt wicks moisture and prys the bushings tight - causing a stiff steering system...this is common on yamaha and merc engines - these points need to be lubed,monthly...