Engine shaft leak

[TedStrat]

Another great sail today in the northeast with great weather and steady winds. Unfortunately, I discovered some water in the bilge. Have any of you guys had experience with a raw water leak coming from the back of the engine-at the transmission where the shaft comes out.  It seems to run down and drip off the shaft -about 1 drop per second. I'm fairly sure it's not a packing issue since it's above the nut by about 3" or so. I have a Westerbeke 12d2... The transmission is raw water cooled. Any thoughts out there would be appreciated.