Plus 1 on the Maine Sail post.
I had to build a panel because the original Westerbeke one was too big for my location.
I placed all the gauges plus two buttons – glow plug and start.
The key and the buzzer were inside the cabin and yes, I could hear its high-pitched sound well with engine on and the companionway closed.
I only used the key because it came with it - it was always in place, otherwise I would have used a switch.
I used 1/8 inch phenolic for the base rather than ply or plexiglass, as it is resistant, more suitable for electrics and easy to cut (look up its specs here PHENOLIC
). I bought a small off-cut for the purpose.
I did not have an opening cover, the panel was totally waterproofed and was installed/screwed from the inside. For the cover I used a piece of ¼ inch acrylic with screwed and bedded with Dow 795. If I needed to service it I just unscrewed it from the base from inside.
Worked well and was always dry.
You can find push-buttons for the glow-plug and starter that has a rubber ring to prevent water ingress - I had that mounted thru the plexi cover.