To answer your question - yes, for a single night, if it's pretty nice weather, you'll be fine.
The primary differences between ski/mountaineering gear and sailing FWG derive from the immense difference between the activities. Skiing is an active sport, and for mountaineering, weight is critical, so the designers strip as much weight out of the gear as possible. Also, hiking and skiing are exercise, so breathability takes precedence over weather protection.
Watch standing involves a lot of just sitting and looking around, or steering, or a little trimming. Not much exercise to keep you warm. Sitting on the rail in cold weather would be even worse. You need heavier stuff.
I found this out the hard way when I did an overnight in spring in the gulf of Maine with my Arc'teryx ski/ice climbing shell gear. I was wearing a lot of clothes underneath, and was still cold.
So I got real offshore foulies, the difference is amazing. Now I just snuggle my head down into that tall, fleece lined collar and baby, I'm toasty for hours.