Motorguide loose steering

[juggernot]

I have a MG FW46FB from 03. It lost some ball bearings in the lower/shaft race years ago and I replaced them w some free ones from a bike shop. I have a slight bit of vertical slop in the shaft and plan to tighten the top nut a bit. My issue is the footpedal/motor will flop back and forth when I'm trying to steer and wakes are rocking the boat and me in the bow seat. How can I make it tighter so it will stay put? will tightening the nut on the top of the shelf fix that, or is there a friction mechanism on the cable itself?