Ms. J. Technicalities aside, why Gilligan's Island? Nautical theme? McHale's Navy has been suggested but why not The Love boat? Mork and Mindy (Mork arrived via space SHIP), 3rd Rock From the Sun and My Favorite Martian likewise. Don't even get me started on Seinfeld, Friends or Frasier-Rubbish all. (MY opinion).
If one pursues the SHIP theme even further....Star Trek (in all it's manifestations), Star Wars, or Battlestar Galactica.
Either self appointed titles or an "out" option is the way to go although I think, with all due respect, newbie or new member should be retained for a period of time. 25 posts perhaps? THEN the new member titles themselves or not.
As to post count? Why not? As has been mentioned, a new member should be able to sense in fairly short order what information, NOT based on post # to filter and use. Hopefully they will avoid any mistakes, even minor, following erroneous opinions/information.