This idea has just popped into my head, no idea if it would work but don't see why not.
Go to your local hardware store and buy one of the lock n lock boxes (o ring seal with lock catch on each side) they are cheap as chips and perfectly watertight. Get one big enought o fit over the gauges (obviously).
Cut a hole in the lid so the gauges poke through it and then screw/seal the outside of the lid to the inside of the console around the gauges. Then you can simply take the box and lock it to the lid thus creating an easily removable, cheap and waterproof case for the gauges/electronics.
In fact thats such a good idea, i might do it myself