Pulled the floor boards.
Found mud, sand, 2X4s ( ?? ) , lots of small pieces of aluminum welding wire
and a few cracked welds on 3 ribs in the aft 1/3 .
Lots cleaner now, need to get some welds repaired.
Pulling wasn't as difficult as I thought.
It was tack welded on the far aft & forward ends at the seam.
Had 2 stripped off screw heads.
Most of channels were blocked or semi blocked for water to drain thru fast.
Vacuumed & hosed it out.
Plan to get the welds repaired sometime this winter.
When I do it again, I'll do it outside & pressure wash it.
Over filled the 5 gallon bucket several times . Ended up with a cleaner shop floor also, when all said & done