Isolated 12V power supply
The high Amp 12 Volt power supply in the boat is really a powerfull source of electricity which should be isolated from the server supply. Even though the 12V safe to touch it is not safe at all when it come to any kind of short circuit. I do believe that the power supply of the yacht server should be isolated from the rest of the 12V system in the boat. This is easily done by some DC-DC power converters that provide galvanic isolation (usually 500V or more). In this way there is at least some safeguard against frying the whole computer setup with sensors etc.
The pictures how two modules that take from 9-18 Volt input and provide 5 Volt and 12 Volt output. The power is limited for these devices as they are small switched power suplies which use a high frequency transformer to facilitate the galvanic isolation. They are happy with a few hundred Volt potential between the input and the output potential.
For my us there would be no problem if +12V from the boats power supply where to come in contact with the 0V (or local GND of the data system). Problems likt this might arise when sensors are connected. Some of these sensors etc require 12V supply and that could bring the boat's 12 V suppy GND into the computer system 0V and pave way for potential problems.
By isolating all the power supply for the server/data system the potential hazard is greatly reduced.
Below is shown two examples, one 15W 1205 for powering the Yacht server and a much smaller 1205 for powering the wireless temperature transmitter.