There are many 3D printers on the market from the cheap
$200US kit versions that primarily use ABS and PLA on up to the $500K+sintered metal ones that can produce a working rocket engines that NASA has been testing and medical
The hobby models that CAN come fully assembled would be and are great for prototyping virtually anything but keep the practical usage to non structural/ critical items. Knobs, hinges & latches
for smaller items.
The problem isn't the plastics used but how they are laid down.
Fused deposition modeling that the hobby printers use is basically like a hot glue gun squirting out a bead(like 12# mono filament line) of plastic, bead after bead, layer after layer until it becomes your finished piece.
The failures most often attributed to 3D printing come from those layers separating.
Folks that have A LOT of experience with them can churn out all manner of quality goodies, even very functional NYLON gears, bushings and the like.
On a boat you have many potential issues.
being the first and the HOURS it takes to print a piece.
The plastic involved are actually somewhat hygroscopic and need to be kept DRY until used or the steam created when printing will not allow for good layer adhesion... then there's print speed, temperature, layer height, %of infil and the list goes on.
I love my printers and have fun with them but from a practical standpoint I wouldn't bother keeping one on board.
3D Parts could work in a pinch but the current
state of technology would make it impractical on board.
When you are back home for the season get a printer and try it it is fun and not that expensive....depending