I am not familiar with your fridge, but I am certified in HVAC
so take that for what it is worth.
To start, has your system been working and now it has just started getting warmer? If so, has anything changed when this happened (sailed 600 miles south, built a new bookcase, get a spider infestation over last weekend, etc)
How old is the system?
Your freezer should be able to make ice at the very minimum, and I would expect it to keep ice cream hard (0F) if it is running properly.
To begin to fix the problem, the first thing is to make it as easy as possible for the heat to get removed from the compressor
and condenser areas. Start by cleaning
all of the dust and dirt from these areas. If you can see and reach everything by hand then just use water
and rags. If it is hard to get to use a vacuum cleaner with a thin extension wand. If there are coils you cannot reach but can tell they are dirty, the ultimate weapon to clean them is an electric
leaf blower but first cover the inside of the boat
and blankets as it will put the dust and dirt -everywhere- !!
The cabinet temperature where the condenser is mounted cannot be over 90F or you are guaranteed to have issues such as yours, so after everything is clean take the temperature several times to make certain yours does not get that high.
Also, the cold plate in the fridge needs to have unrestricted air too so make sure there are no bags of food
stacked around it as you can get frozen peas that are 0F on one side and 35F on the other side. Check it also for any ice build up.
I have found the absolute best tool for measuring temps to be the "non-contact IR thermometers" that are sold
online for $5-$25. They are great for so many things in addition to measuring fridge temps- oven
baking temperature, where you need additional insulation
on your boat hull
, misfiring cylinders on engines, hot bearings on electric
motors, etc. Lots more than just helping you out to fix your fridge.
Anyway, to recap for your fridge first clean out all the dust and cobwebs and make sure the plate is uncovered (if it is a hollow design make sure something has not fallen inside it and is blocking airflow). If the air around the compressor and evaporator feels too warm put a small fan on it to see if that makes a difference to the fridge temp.
Hope that helps!