So in my quest to find the last of the cabin leaks I have (hopefully) run it down to the porthole, after re-setting most every other fitting with new caulk. Pulling the thing out, though, was a task.
After more hours than I care to admit, including use of a pry bar, hammer (with wood block), butter knife (on the advice of a house window guy - useful for cutting caulk out) and significant sailorly language I grabbed a bottle of Everclear from the cupboard. Back in the day we used this 95% grain alcohol to extract herbs for tinctures (really). Now I was going to see if it would soften the caulk and if not, soften the sailor. It actually did soften the caulk and out popped the window. If you find yourself in a similar situation, go for the alcohol early! I now wonder if it would have eased removal of the horn earlier in the season, though the caulk there was of a different variety.
I don't have the heart at this point to run the hose over the cabin to see if I finally have it, and may tarp up the boat before the next significant rain...