This is what I was planning to do on my stern rail, probably after cutting the split a bit wider for deeper penetration, and to get clean wood in the area to be treated. Either that, or shaping the split and then filling with a thin shaving of teak, secured with epoxy.
I apologize for hijacking the thread with my own crack issue. In your case, as jsai says, the correct solution is to completely remove the caulking where the gap is and then fill with polysulfide caulk, which is made for that specific purpose. The same stuff used on teak decking. Research the preparation requirements and application recommendations. Once the seam is caulked, you can then finish the cover with your preferred product.
Yup. The original little teak trim strip across the back of the cockpit had cracked even before we bought it. Epoxy forced into the crack would only provide a smooth surface for a year or so. I lived with it, since it was ornamental, and as part of the 2021 re-fit it was replaced with a high-density plastic piece.
