An interesting sidenote:
I looked on line for a new thru hull fitting to replace the one that broke. (It was plastic, like every other one I've seen, at least on aluminum fishing boats) Every plastic one I checked stated "not for use below waterline". Guess Duracraft ignored the statement. So, for an additional $8 I ordered a stainless steel one.
It came today. Guess what it said on the package.
"Not intended for use underwater"
I think now that is a CYA in case one leaks.