I am almost ashamed to admit it but 2 years I did something not smart, replacing my propane hose - that brought me in somewhat similar experience (clean salt water, not oily though - i tasted it was really puzzled:-).
J/30, model 84 and after, have a propane locker starboard size of the cockpit. The copper 'through-hull' was actually at the bottom of the propane locker - which happen to be under the water-line on port tack.
I had just removed the original sealed locker-through copper tube by a loose not sealed traditional propane hose. It took me a while to find it out... went to all hole, seacock, water tank, anchor drain, stuffing-box... my wife found it...:-)
Last edited by Georges; 06/24/12 11:25 AM.