Q: The caulking on my boat is dirty and has mildew or black stains on it. How do I clean it?
A: Very gently is how you clean caulking. The main thing you need to remember is that it only lasts for so many years, so try to clean it gently every time you wash your boat, but once it starts to turn black, it’s probably time to replace it soon anyway.
While you’re caulking is still new and white, use a soft brush or rag with a gentle boat soap to clean it. Never use anything with course bristles otherwise it can start to tear into it and lift it from the seam that it’s sealing.
Once you start to see stains in the caulking that don’t come out with soap and water, you can try stronger cleaners such as Simple Green or a black streak remover spray with a soft brush or sponge, but if that’s not taking the stain out, just let it go. The whole point of caulking is to seal the “seams” of your boat. The last thing you want to do is scrub so hard or use something so harsh on it that it removes the caulking along with the stain. Best to just have those areas re-caulked on a regular basis.