Here's another option.* We put in a SeaFreeze custom unit*3+ years ago and like it.* They built the unit to our dimensions with added insulation.* There's separate compressor for the freezer*and refrigerator.* The refrigerator is about 6 cubic ft and the freezers about 2.5.* Not cheap though.
http://www.seafreezeinc.com/marine_refrigerators.shtml