There are two adjustments, there is a set screw under the plate that puts some tension on the lever, and the screw that holds the lever on can come loose too. It came off in my hand at full throttle when the boat was new, chick was on the back and flew off, had to push the stop button on my keyless ignition to kill the boat. Actually, my pal Thom had the presence of mind to do so, I was dumbfounded with a shift lever in my hand:) It just needed to be reassembled correctly.
I did find a drawing and stuff for the shifter assy, not sure if I ever scanned it and posted it. it is a Morse shifter, can't remember what model but I found some PDF's on line that described all adjustments. There aren't any. I wanted to adjust the throw so that I could achieve WOT with the throttle extension necessary to make PP work. Unlike other shifters, there is no adjustment for the throttle throw.
I'll poke around the innnernet and see what I can find........