Seacocks are ball valves, but a ball valve screwed to the top of a thru hull scoop is not a good seacock, but that is how my Grady, and most are done.
Lot of articles about why it is a bad practice, here is one.
Glacier, yes mine are thru bolted with washers and also the big nut that screws down on the threaded pipe. Mine were factory thru bolted, I just installed all new hardware when I redid mine.