I did my own install of a Frigoboat unit with the "keel cooler" option about a decade ago. Very Quiet (no fan) and efficient. The install is very fiddley work, in places where one can put only one arm and shoulder at a time, and some swearing will be needed.
After wising up and putting a gasket around the lid, almost zero condensation or frost on the evaporator plate.
I have some pics over at EY.org in a refrigeration thread. PM me for a link if wou wish.
Take your time, diagram out what your boat requires, and be sure to buy the parts kit from a reputable supplier who can answer your questions when you are upside down in the boat with a drill in one hand and cell phone in the other!
Frigoboat Home Page
These folks were extremely helpful and patiently answered all my stupid questions.