Yes the top ones have nuts on the inside. The bottom screws are self tapping screws that are supposed to tap in to an aluminum plate. I discovered that the center floatation compartment, under the center ballast bag, was water saturated so I assumed that it was the same with the aft ones. I took a hole saw and cut a 4" hole in the floor on each side (aft ballast bag compartment). Both sides where wet and on the port side the aluminum plate was loose on the floor/bottom. I put new bolts and nuts and installed a waterproof inspection hatch cover.
2004 Supra Launch SSV
1991 Ski Nautique