Rudder Movement

I have a 92 Nautique.
Towards the back end of last season, the steering became increasing heavy and difficult to turn, it was especially difficult to turn to starboard whenever any level of power (prop rotation) applied. With the Prop not turning the steering could be turned freely in both directions using just a finger.
The boat is out of the water now , and I have inspected the rudder for damage, there is none, however there does seem to be some play in the rudder side to side.
My question therefore is what could cause the heavy steering? And how do I recitfy it?
If the solution involves removing the rudder from it's housing, is there a manual available with the breakdown of the parts of the Through hull housing and how it goes together?
Advice please!!
Pete

All the above are things to look at, If it turned good before there is certainley a problem. One bad feature was that the props were too close to the rudder. Because of the style of rudder the force of the water generated puts a terrific strain on the rudder makeing it harder to move. Also the props were too far away from the back of the strut which also caused excessive vibration, and the above condition. This was changed in 1997 putting the props closer to the strut, makeing more uniform.