I thought we were just talking about the sink drain.But, one of the outputs I am sending overboard is the shower sump output. That is not a gravity drain.
But, yes, in the case of a pressurized hose, that would change things. While the plumber's putty would solve the issue, it's not like it's challenging to use the hose cuff, either.
Funny thing is, I don't recall hose cuffs actually being used at the thru-hull barb. It could just be that I don't remember one way or the other... but it has me curious, now, if they're used there.
EDIT: There's no mention of it in the parts list, but truthfully, that's not always indicative of "is it or isn't it used" as sometimes some parts are not shown.