Dave's right! The yard manager does not have your safety in mind, only his profit margin. It takes more experience to put in a seacock,
It takes more experience to install a flush thruhull than a mushroom.
To get the handle orientation correct on a ball valve, the guy tightens it a little more or a little less. On a seacock you have to trim the tail of the thru hull and you have to think where the small fastenings go in relation to where the handle will end up. You probably have to put it together dry a couple times. The backup pad has to be 90 degrees to the thru hull - you can cheat with a ball cock. On a cramped boat, the handle has one place it can go plus or minus one degree.
The ball cock on a thru hull tail piece is an accident waiting to happen. A proper whack of a "tool box" against it could break it off right there at the exposed threads, which have relatively little meat on them. With a smidgen of dezincing your new sanitation tubes won't mean a thing. Especially if the last time you changed your seacocks was in 1978.
It's a big if, but if you ran the ballcock down to the thru hull backing nut so it would be less likely to "tip" when hit, that you could argue ok. Seacocks with their wide bases were designed for secure installs. Suggested on another post that a first class seacock install would not necessaryly require the flange fasteners go thru the hull. just into the backing block.
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