Most boat hulls have a (fairly thick) layer of fiberglass sealing and holding the deck half to the hull half... after removing the rubrail (and any rivets/screws), boat repair shops use a saw to cut thru the inner layer to seperate the halves, then they just apply a new layer of fiberglass to the joint when they put them back together. On boats, the halves have to be seperated mainly for transom replacements (my jetboat will need this done at some point, there are a few soft spots starting to develop in it's transom it costs around $1K I've been told to split it and replace the wood in there).
Anything can be taken apart if you are willing to cut on it enough! But in the case of boats/PWC's, it isn't something you can do with just a screwdriver and wrenches.
I fail to understand though why this RXT's hull needs to be split just to fix the gelcoat... if you have alot of bottom work to do, just turn it over (drain the fluids, build a padded stand of some sort needed to support it's weight upside down!). If there's damage to the fiberglass (like cracks or breaks) going thru the hull to the inside, then remove the engine... it's not that hard. There's no reason you should ever have to split a SeaDoo PWC hull apart to my knowledge.
I occassionally see good RXT hulls with blown engines for sale on Ebay, or parted-out ones without an engine. Not often, but they do come up from time to time you could transplant your power system to another hull if you Watch Ebay for awhile till a hull you like comes up for auction.
Regards.
- Michael