4-TEC Reverse Bucket Adjustment

[jjk]

The reverse bucket on my Glastron 187 GTS will not lock in the forward position and seems to be partially in the jetstream. To adjust it, I have disconnected the cable from the bucket, removed the cotter pin and plastic cover on what I think is the adjustment mechanism and tried to turn the threaded fitting, which I think would adjust the cable length. I cannot get the threaded tube/fitting to turn as space is very tight. Is there a special tool for this? Or am I doing something wrong? Is there any other way to adjust this? Please help, thanks.