I'd say that, cannon-wise, centaurs are pretty unlikely, since I'm fairly sure they were created by the Master's mad scientists. On the other hand, I don't think anyone would object if they happened to be terror units designed by the enclave, later unearthed by the Master... Perhaps one of the vault experiments even involved locking people in a vault full of centaurs, to determine if they could live alongside such creatures.
My thoughts on a Hawaii setting in fallout is that the lack of land area and food stockpiles wouldn't really encourage raiders, though tribals could certainly engage in raider activity from time to time, even though they would need to rely on hunting and gathering as well as light agriculture for survival for the most part. Hawaii's soils are fairly fertile, but most of the existing seed stocks are for cash crops, rather than food crops, meaning that civilization will tend to be fairly tenuous. The Great War likely depleted pacific fish stocks, but if FEV, radiation, or changing ocean currents brought some kind of edible superfauna to the surface, then hunting the megasharks/hypersquids/gigantic jellyfish would provide some kind of help to coastal communities.
In a pinch, algae farming might also work, if the ocean isn't excessively toxic, and/or an edible form of algae capable of handling the problem can be found. I imagine that fresh water is reasonably easy to find in hawaii, since in the worst case scenario, one can simply locate a volcanic fracture point to build a distillery for seawater. Even if there isn't any practical use for the ocean, it will still support the most obvious sort of raiders for Hawaii: pirates. The limited land area of Hawaii, especially that not screwed up by radiation or chemical/biological weapons, means that raiders can only find enough communities to support their existance without getting pushed out on the biggest islands. Everywhere else, they'll need to come from and then dissapear into the sea, like vikings.
Most pirate crews could likely scrounge and/or refit an old metal hulled boat, but I doubt they could repair or easily power the fusion engine, and would likely dump it if they possibly could. Sail power would be more efficient, and would almost certainly be relied upon by any legitimate fisherman or traders, though pirates might want to rev up an engine to approach becalmed vessels. If the wind patterns in Hawaii post war leave the air still too often, the pirates might even retrofit vessels as modern day slave galleys, though this seems more like a tactic for extremely strong viking type pirates, or pirates too stupid to figure out how to get a ship going in the right direction under sail. The art of sailing likely wouldn't be something pirates would be too intimately familiar with, but a combination of guesswork, old pirate movies, and surviving pre war knowledge would give the pirates a decent idea of how to rig a ship.
I'd imagine a lot of ship to ship combat would be resolved using energy weapons in place of cannon, though boarding actions would eventually be the order of the day. Piratical raiders likely wouldn't invent scrap metal armor, but might find ways to make combat armor lighter, or create reinforced leather hides, perhaps out of an exotic creature to help out in that sort of setting. If the post war ocean is possible to swim in, surfboards, possibly equipped with sails, could be used for boarding actions and inter-island transportation, which might create another class of surf-raiders paddling on their boards to get in and out quickly. Speedboats and Jet-Skis would essentially be the ultimate vessels for attaining mastery of the sea, but getting the fusion cells would be hard, and keeping them in repair even harder. If anybody got a pre-war US navy vessel online, even a frigate or a mothballed WW2 destroyer, they would likely become undisputed master of the Hawaian ocean. Of course, US navy vessels probably ran on petroleum, so keeping the doomsday device going would take some doing. (On the other hand, the idea of an entire island empire keeping its subjects in line to produce ethanol to run a Cruiser is kind of cool)
Well, hopefully that's not stepping on some toes, Inerrant, just my thoughts on what Hawaii would be like in the fallout setting.
