That's why I was leaning towards numitrons. Pretty robust. It's a pontoon so I'm really not too worried about mechanical shock. However I also have some small HP LED displays that would look great.
I've identified a couple of gauge housings, but I'm having trouble finding the drawings/dimensions for them. I've picked ones that match the existing gauges in my boat.
Once I have one in hand, I'll take the next steps towards the actual clock design. Considering a GPS disciplined design.