Just pretend it's Nascar, go fast, turn left, go fast, turn left, etc.
But seriously, probably bad rudder bearing or packing. There should be either a bearing or a bushing behind the seal the rudder shaft goes through, this could have gotten wet, rusty, crudded up which would make it hard to turn. Not sure what boat you have but most are pretty similar. Just pull apart until you find what's bad... But first I'd disconnect the cable and turn the rudder by hand just to be sure. You'll probably feel it not so smooth when turning it right by hand.