The argument for ball valves, from an installer's perspective, is that they are lots cheaper, you could keep a bunch in inventory for a lot less than flanged seacocks...and they are easier to install.

The still-current argumant against is that all that weight and vibration load is sitting squarely on the threaded neck of the thru-hull. This is really bad if the thruhull meets a hot marina and there is an electrolysis issue, and can be bad if something comes adrift in the boat and goes slamming into the thing. It takes a whole lot to snap off or corrode thru a seacock, even if the thing is very pink and very old. The head discharge seacock in the Triton was both of the above and very stuck, to boot. No thru-bolts, either, just gooped to the glassed-in plywood backer. After I took out the thruhull barb, I still couldn't get it to budge. Had to finally smack it with a BIG hammer to get it free, but it didn't break.

Last summer I replaced all the thruhulls in a 1978 Pearson 30, as well as replacing all the fiberglass tubes with thruhulls. There were an number of simple thruhulls with ball valves in that boat, and using nothing but a pipe wrench I had no less than two of them break right off before the ball valve would turn to come off.

It wasn't THAT big a pipe wrench. I'm not THAT big a guy. I wasn't pulling any too hard, and I wasn't pulling at a goofy angle. There was no pinking that I could see. These things scare me.

Lots of boats have these installations like this, certainly more than have proper seacocks...because it is cheap and fast and there is no regulation that forces the maker/repair facility to do otherwise. I'm sure it works great 90 percent of the time, right? I just don't want to be aboard a boat that becomes the smaller number.

BTW...the one that broke off the fastest...the valve was turning, albeit with difficulty. All of these broke jaggedly (I think there were actually three that did) well below the valve and well above the hull. So...right next to this one...is where the owner kept his toolbox!

That all said, I'm sure what you have there will work...it wouldn't be my preference, but it will work...just treat it tenderly.

Best,
Dave