Can't say I've ever tried it, but this seems extremely doubtful. Even new cars go rusty pretty quickly if kept where sea-spray reaches them, as I know to my cost. If you need quick-drying paint for steel, use something like Blake's epoxy primer, which is touch dry in a couple of hours on a mild winter's day in the UK. Five coats offer excellent protection, but for looks it can be overcoated with polyurethane when the weather gets better.
You can use acrylic automotive finish for outside parts of boat, 2 K system ( base color mix with Clear and than add hardener)and it will be better than Polyurethane, but price performance is questionable as PU have twice lower cost.
Rule is: UP - Polyurethane
Underwater - Epoxy paint over Epoxy primer
Bilges - Epoxy paint
I would be very wary of using car paint.... I used Jotun "Jotamastic" epoxy followed by their "Hardtop" two-pack polyurethane on my steel boat. They say you can use the epoxy at temperatures down to +5 deg and I think (not sure) that the polyurethane can also be used down to that temp. I haven't used it at a temp as low as that but I have used it at 10 deg. The epoxy took a couple of days before I felt it was hard enough to rub down but the polyurethane top coat dried much more quickly. On a warm day (20+deg) it actually goes off too quickly and at ten degrees.... I didn't time it but I would guess that it was touch dry in a couple of hours though I wouldn't walk on it for 24 hrs or more.
I have been very pleased with Jotun, it is easy to use and VERY tough.