I want to repair some floor beams and pull the water tanks for
cleaning/inspection. My boat, a Swift 40 built in Korea in 1980, has
ribbed stainless nails instead of screws under the plugs. The teak
planks are grooved on both sides and the white wood (spruce) is kind of
cruciform, although each leg is the same. =||=
OK, How can I pull the floor up with the least amount of damage?? I
would like to end up with screws in place of the nails.

I'm thinking of pulling the 4 floor hatches and then sliding a hacksaw
blade in sideways and cut as many nails as I can, then lifting as much
as I can, and cut some more.

Also, any ideas how to get the white wood out of the grooves? after
each plank comes out the white wood will, hopefully be intact and
probably stuck to one side or the other. Boiling water?

Norm