by GreenLake » Fri Jul 17, 2020 7:09 pm
David, let me make sure I understand what I am seeing in the photo. You mention an inner space (bilge) between cockpit sole and hull. So, what we are looking at in the picture is not the hull, but the cockpit sole, or the "roof" of that inner space. However, the CB, while it has a nice "cap" isn't fully enclosed, so what we are seeing there is the actual wall of the trunk.
So, where can water get in? It ends up in the bilge, but when you fill that inner space with water, it does not exit from the hull (meaning the hull below the level of the cockpit sole is water tight). (Including the plug: as a leaky plug would also allow water into that space).
You reported that water seeps around the base of the CB trunk into the cockpit, after you filled the inner space. So, I concur the seam is probably not watertight. But even if you caulk that seam, will you have stemmed the leak? You could try some white 3M 4200, but because your cockpit is off-white it would show.
Now, while you are sailing, is there any water puddling in the cockpit? If yes, sealing the cockpit sole may keep that water out of the bilge. However, if there is no puddling, then you still need to look for a source.
Once the CB gasket gets old, you may notice a leak there, however, it would leak into the cockpit first and should be visible. (Do plan on replacing that gasket regularly; replacements are sold by DR Marine).
If you did not see any water in the cockpit while sailing, your source would have to be higher than the cockpit sole in the hull (including hull-deck joint) or it would have to be something that acts like a one-way valve, letting water in, but not out (or a crack etc. that opens up only when the boat is being sailed).
~ green ~ lake ~ ~