Very few domestic or RV units are made to stand out in the rain or sea spray.
"Marine" perhaps a bit better , but the simplest is to simply build a case to hold the unit.
Our RV propane reefer was made to be inside an RV , not outside in FL 24/7.
A very simple box holds the unit on the after deck.
Yes the outer door has to be opened firrst , and yes the RV vent system needed to be installed on the top of the box.
The 45? year old unit did the loop and is still working flawlessly .
High and dry during the summer deluges.
With a bit of planning the box could hold more insulation to reduce the system work load.