Run it through the Mercury prop selector online. The lowest pitch possible without over revving, tune the motor up, install trim tabs and say a prayer. It's very under powered for that situation.
I've used Tear-aid with lots of success as long as you follow the directions. Clean the area real well, apply some warmth to it (hairdryer) and use good pressure to apply.
There is one ramp on Lake Cumberland (KY) where I experience the same thing. I launch solo so I have to back in far enough to pull off without anyone dumping me in. The ramp is very shallow most of the year. This is of course fresh water. My jack has the black plastic cap so I can remove and...
Can't tell from the diagram, I'm an A1G2 guy. Is the tab washer you reference above the one that locks the prop on after it's tightened? Just tryin to understand. So it's believed with a counter rotating prop it spun loose and this is what caused the water intrusion?
I'll add bellows, shift cables, u-joints, alignment, breaking trim sender wires, multiple avenues for leaks requiring yearly drive pulls and the ability to be a circus contortionist.