The epoxy job will last forever... provided you do it right.
Dry the area. Run a dehumidifier inside the boat, vacuum with a wet-and-dry vac, dust, blow, whatever you can do to eradicate the water.
When it is fully dry, seal up the bottom, using tape or something that will (temporarily) hold back epoxy.
I prefer WEST epoxy for everything; though I have used MAS and others. Mix it up using SLOW hardener (206) and silica powder, not so much that it won't flow as a liquid. The silica keeps it light.
Using a syringe (best) or squeegee/spreader (okay if the mix is more fluid), work the epoxy/mix into the gaps from the top. If you are filling wider areas of the deck, you should drill 1/4" holes about 5/16" deep in from the top of the deck to allow the epoxy in. If you are astute you will drill these only in places that are painted in nonskid and then, when you're done, just fill them neatly and paint them over.
I do not recommend doing this with the chainplate in place. My 'chainplates' are angled SS plates mounted to the aluminum toerail. If you remove the chainplate(s) first, you can fill the whole lousy opening and later recut the slot for the chainplate. This is best-- a nice new clean cut through a properly-done, fully-cured epoxy laminate is the very best new starting place you can hope for.
This is the method I have used on Cherubini 44s (with their 30-year-old plywood decks) as well as on my own H25. In fact I was just doing a new place today. (Mind the drips below. Every few pumps on the epoxy, you should go below and check. Today they dripped into the drill-bitt box-- doop. I use masking tape to stop the seeping through the underside skin and scrape it off when it's dry.) Done right, it is the easiest and surest way of solving the problem.
I did begin to fill some holes in mine once and discovered there had been water in there. Fortunately the epoxy sank to the bottom and drove the water up to the top and out the fill holes I had drilled for the epoxy. It looked like baby spitup. This was lucky for I had not expected to get out of that mess alive. As far as I know the epoxy cured anyway. The deck in that place is solid now... and I have assume there's no more water left in it!
