Looking into buying an aluminum Jon boat.  There are bunches of them on Craigslist.  

Is a V hull any more stable in the water than a comparable width flat bottom??

Is there such a beast as a v-hull john boat?  Never heard of it.  Just curious.

There are dozens on Craigslist. Example....http://richmond.craigslist.org/boa/957358874.html

Is it just mis-named?

Jon boat hulls come in 4 different designs

Flat: very stable at rest but produces a wet rough ride

Modified V: very stable at rest and handles chop better than a flat

Full V: tipsy at rest but has a smooth ride

Pad: same type hull as a high performance fiberglass hull

The stability of a Jon boat comes from the bottom width not the beam  

yes and yes

Modified V is what you want.

I have a 14' starcraft semi v and it's EXTREMELY stable at rest, and when moving.