Floorboards have now dark areas

[pelissima]

My floorboards have recently developed extended dark areas.
I guess that occasional dirty oil and diesel accidents in the bilge were absorbed and finally found their way from bottom to top.
I can live with it unless someone has a bright idea for a remedy.

 

[Elemental]

Our friend Oxalic Acid again?

 

[doug748]

I have two dark patches on that part of the floor that follows the curve of the hull. They correspond exactly to the points where people step in order to go forward in the boat.
The ply seems to be holding up and they have got no worse, I suspect the staining (or whatever it is) will be evident right through the material. As you say, I just live with it.