2001 Tracker Tahoe 204 loose captains seat

[Bkings]

I have a 2001 Tahoe 204 deck boat. The captains pedestal chair is loose at the mount on the deck. Looking back from the ski locker I can see the nuts through a ¾ inch gap between the floor and rear ski locker bulk head. There's no access that I can find directly to the under floor area. I've tried tightening the screws but the nuts just turn in place. Any ideas how to access this area or tighten the nuts?
I'd like to reinforce the floor area too if possible.

Any help appreciated.

I'll post pics when I get home.

 

[alldodge]

Howdy
Most likely the deck is soft and needs replaced. It may even extend further then just the deck.

Need to start cutting out the deck until you find solid wood with no moisture. Once there can replace the wood and fiberglass.

 

[Bkings]

I'm not sure there is wood in the floor. It would make sense that there is but looking under there I can't tell. I might wait until this winter to dive into it

 

[alldodge]

I'm sure there is plywood under, and its covered by fiberglass
The seats would be held in place by wood screws or lag bolts

 

[Bkings]

It's held in place by screws with nuts under the floor. I can see them. I just can't get to them.