Owner, but not expert
Eric - I own a 78 O27 , but make no claims to expertise. Mine too leaks around the port side shrouds, especially the upper. Look thru the archived forums and I think you'll find this was a fairly common problem, though wether or not it was unique to O27's I can't say. The chainplate for the upper shroud attaches to the "main" transverse bulkhead, so leakage will cause this plywood structural member to rot eventually, requiring replacement. Also there is probably rot in the balsa cored deck around the chainplates. Both conditions can be repaired relatively cheaply IF you have the tools & skills to do the work yourself. Farmed out to a yard and I expect the bill would be quite large. Your surveyor should be able to elaborate on that, plus the other concerns you've expressed. $ 6K (asking) doesn't seem like a lot of $$$ for a 27 ft f'glass boat with a 2 cyl inboard diesel etc etc, but your market is very different from mine, so maybe it's just a fair price for a fixer-upper. The porta-potti noted in the listing sure isn't a plus, and Loran has been superceded by GPS. The galley looks nice though. The 27 is considered by many to be a fair sailer, but it sure as hell isn't a 'blue-water' boat. I guess if you're on a tight budget you could do a lot worse, but much depends on the amount of abillity, time & effort you are able to spend on the boat. Good luck
