On further thought.......
It could be pretty easy to take the standard method used by the K boats with their thru-hull shaft, seal, etc. and just weld a threaded nipple on the inside of the hull and add a ball valve. The existing handle/shaft could be cut off just inside the hull, add a spline or nut, and then the handle/rod could still reach through the ball valve to turn the shaft.
I know....you guys think I'm paranoid about leaks.
Always dry, Frank D.