When you get the old thru hull out you will see that the inner liner & the hull are thick enough to support the tightning. I don't think you can get access between them to reinforce anyway. You don't need to torque it down. Use 4200 vs 5200 cause you might have to remove it some day. Like I said just keep a watch over it.

NOTE: You might have to grind down the Gem's outside flange to create a flat section angled so it will fit tight againt the chine. Just dry fit it a few times before you lock it in place.

Thanks Chuck, no worries about the chine on my 18 SF since the thru hull location is a good 3" above & away from the chine.

mine was leaking when bought my 77, was def brass. glassed it in from outside hull and glassed in hole in box to brass drain. and drain to bilge now only that box with another hole.. I did have a pro do this, at same time had a leaking center stringer (wood core) filled with water from years of water I think accumulating in bow when boat not tilted up on trailer is my best guess.

I don't put fish in that box. if I decide to do that, I have pie plate access both casitng deck box and forward of console box and would plumb hoses to a macerator. not planning that either.