Marine radios are clear coated for their circuit board. Truthfully,
I'm not sure how much that helps, but if I were mounting one in my
cockpit for a motorboat, then I'd really consider it. I know that
there are many components on a regular radio (which I just had to
replace) like a grounding plate which had rusted to dust in the saloon
of our catamaran.

Frankly, getting a marine version couldn't hurt anything assuming that
the price isn't that difference. Here's a link for 9 different
models from Crutchfield, they seem to be maybe around 20% more
expensive than the others, so it's not a bad choice if it has the
functionality you are looking for.

http://www.crutchfield.com/S-rbeZBua...p.asp?g=221050