I don’t know, stains were there when I purchased the boat. I spilled some coolant in another location and didn’t wipe it all up and it looks just like these marks Maybe some sort of Teak treatmeant would help?
Let's just call it Lemon juice then. It has bleached, dissolved or eaten through either a very thin veneer or decorative film. If it's wood you may be able to stain it with Minwax using a cue tip or a very fine paintbrush. I think it might be a decorative film and the substrate could be a substance not found in Nature. That might not take the stain. But I don't see a down side of trying it.
Catalina put me in touch with the manufacturer of the sole. It’s basically a formica floor. They said once you’ve eaten through that outer veneer you’re pretty much screwed. I’m going to give the floor color markers a try....
We had a leaking battery drip acid, creating a similar spot. (I also had to rebuild the battery compartment as no battery boxes when we bought the boat).
I suggest to protect the sole when using any chemicals around the engine. Degreasers, certain sprays will stain/bleach the sole. I have a couple spots close to the engine, that fortunately are under cover.