Or you can edit the file CareerTrack.upc in the SaveGames folder. You can start and save a dummy career with the boat you want. Copy and paste the starting information into your on-going career. Make sure you make the event numbers sequential. If you browse a few of the CareerTrack.upc files, you should be able to get a sense of what event blocks you need. It takes a bit of care and observation, but it's not rocket science, either. And submariners ( even simulated submariners
) have a rep for being resourceful.
DO save a copy of any files you plan to change before you change them. Then you will be able to get your career back if things go tango uniform.