Well, I do have a diagram.... but not much to see. I think the square hole may be 45deg off from my diagram, but it shows basically what is there. The square portion of the handle shaft fits through a square hole in the CB and over the years that hole tends to wear. I was able to insert a couple of pieces of wood shingle to tighten it a bit, but that takes a bit of trickery to get the shims in! You might be able to glue in something to tighten the hole.
To remove the CB it is simple as long as you have the boat about 18" or so off the ground with nothing in the way of the CB trunk. Remove the 3 screws that hold hte CB handle in (3 screws holding that triangle plate), carefully slide hte handle out and the CB should slip out of the boat with a thud!