Sorry I don't know the answer, but if it helps–I painted all the under cushion areas with Interlux “Brightside” polyurethane paint. (I may have primed it with “Kilz” as well — can't remember.) It's holding up very well.
Al, I'd be surprised if they used water based paint…….The “old” water based (latex) never really got “hard”….The film strength was not comparable to oil based paints.
Now folks like System Three make water based catalyzed Urethanes that work quite well; in the cool/damp New England spring weather these would go on & cure well….That said it's a “thin application” paint and needs multiple coats. Me, I've used Brightside, Easypoxy & Kirby paint – All with good results…. All oil based 2 coats. Pretty simple stuff to work with.
I know while I was working at Dickerson, Latex paints were unheard of in a boat yard (and I suspect that is still true). I have to second the Easypoxy or Britesides paints for durability and gloss retention.