Hi,
the trouble is, that your hull has been in contact with saltwater and the
salt cristals are in the wood. Whatever you do you will always attract humidity, the wood will swell and the epoxy will break, facilitating more water to find its way in and speeding up the process where
rot develops and finally destroys the whole boat.
The most successful way out is to laminate 1 or several layers of veneer or
plywood (depending on the size of the boat) in strips of 14 cm (again depends on the shape and size of the boat) in a 45 degree angle to the planks on the outside of the hull. Once this is done you've got a strong and solid barrier on which you can laminate with epoxy and fibreglass to make the whole thing strong and watertight.
Important: do not use Polyester for this, but go for epoxy!!!
I have to face this whole process on my boat at the moment, as after 57 years the nails between the planks and frames are giving up, fair enough. My boat was built like this from the beginning, only trouble is that they used polyester instead of epoxy, so, actually fortunately, the whole stuff comes off easily. A process you don't have to go through.
As I'm quite heavy with 22 Tons and will sail to some very
remote areas, I've decided to go for 3 layers in 6 mm
plywood (each layer crossing the one before) and 3 layers of fibreglass with epoxy plus, at least from bow to stern under water another with kevlar or carbon (got to look into these two materials to make sure I get it right).
To understand what and how I mean this, there exists a little film. It's unfortunately in german, but it shows the process and how it can be done. You can find this film here:
Furnier statt Leichenhemd
Also, to better understand it, you can download the book (for free) from the Gourgeon Brothers about wooden boatbuilding in epoxy:
http://www.westsystem.com/the-gougeon-brothers-on-boat-construction
Good luck and fair winds
Dody