Taken from http://www.smallcraftadvisor.com/articles/5-seaworthiness-q-a-a.

1.Unsinkable - using solid flotation if possible, such as thick foam core. 2. Fixed keel
3. Easily reefed
4. Fully watertight companionway
5. Enclosed cockpit (i.e. full lifelines)
6. Full height lifelines (27")
7. The ability to self-right from at least 125 degrees of roll (180 preferable but hard to achieve)
9. Sealed mast with external halyards (to help with self-righting ability)
10. Enough headroom to at least sit upright while on the head (an under-rated characteristic).
11. Sailable (and preferably sailed) by 3 or 4 maximum.
12. Fast enough to get out of trouble (also an under-rated characteristic)
13. Open accommodations to avoid claustrophobia
14. Large enough berths (6'4" minimum) for all crew.
15. Real head with holding tank, chemical toilets just don't hack it in a storm
16. Watermaker
17. SSB
18. All items required for a Class I Offshore race as defined by ORC, if not already included.
A life raft is a really comfortable thing to have around, but difficult in 25ft. I realize I would
probably have to work very hard to get all this into 25ft, but I'd love to try.

   1.  If it is a centerboard boat, find some means of fixing the board down when offshore. Do not
forget to free it up before running into any rocks at the end of the trip.
   2. See item 9 above
   3. Flotation, whether solid or air bags, gives a nice warm, fuzzy feeling when the weather turns
nasty and no land is visible.
   4. Make sure your reefing system is capable of being operated in the dark, in 50 knots of wind,
under a very hard, cold shower, in a bathing suit. Practice this before leaving, it will make your
kids laugh if nothing else.
   5. Make sure your steering gear is bulletproof. If possible, take a spare rudder or something
that can be used as one. Single-handed racers have to demonstrate an "alternative means of steering"
before being allowed to race, with reason.
   6. Motors. If you only have an outboard, it is best to stow it out of the weather, but make sure
you can put it into play in the same conditions you practiced reefing in.
   7. Heavy weather sails are a necessity. With no motion you have no control.
   8. Before leaving, check your rigging, replacing any part showing signs of excessive wear or
fraying.
   9. Check all hatches for watertightness. This is easily done with a good hose and spray fitting.
A pressure washer will do even better, and again, the kids will love it.
  10. Pulpits and stanchions should be checked for condition, and replaced if necessary. If you
don't have lifelines around the whole boat, fit them.
  11. Some sort of self-steering gear can be handy, but is often not possible on a small boat. If
no self-steering, 3 crew are a minimum.
  12. Food - make sure you can store enough for longer than you estimate the trip will take, and
make sure the storage is dry.
  13. The most often forgotten one - PFDs, two for each person by preference, and wear them! The
spares should be stowed below where they are available but out of the way.
  14. Attachment points for safety harnesses should be fitted to allow you to go all the way to the
bow if need be. Please take the harnesses with you.
  15. EPIRB - don't leave home without one. If you can't afford one, don't go this year.
  16. The most useful one of all - hire a surveyor for a couple of hours to check your boat thoroughly
for suitability. It is an extra expense, but he is more likely to find the weak link than you, and he
will be objective. I could probably go on for hours like this, but those are the ones that spring to
mind with DO THIS written all over them. The opinions above are based on a serious offshore passage
(i.e. Newport-Bermuda type) rather than a "cruise down Long Island Sound" scenario. After 10 years
of being involved with the design of single-handed 'round the world racing boats, this is really
the short list, but you did say 25ft. 

R2AK Damage Control