Need advice on securing pulpit

[ranger26]

Hi,
I'm looking for advice on securing the pulpit on an old ranger 26 I recently purchased.

The interior side of the deck is cracked and looks like its in bad shape. Here are some pics of the bolts coming through the deck:

- Album on Imgur

Based on the rust, it seems like water has been leaking through. Does this mean the deck core is likely trashed? I'd like to avoid tearing up the deck if I can.

What should I do to repair the interior skin of the deck? I'd like to build it up flat and add backing plates, any advice on that?

Thanks