Problem solved, water in lines, carb. Both lines and tank were aging but showed no obvious crack or leak so I threw away both and replaced with new as well as non-eth gas from one of the local stations. My best theory is that the tank had a recessed area around the fill cap that opened all the way to one side. I'm sure you know what I am describing, The recess allows water to drain off the tank away from the fill. Well, it would as long as the tank was level or angled down to allow water to flow and not pool in the recess. Our dinghy is angled in the chocks on deck, port side a little higher than starboard. Gas tank turned the wrong way in an angled dinghy made a nice little pool area around the aging fill gasket. This caught the rain water which soaked through into the fuel. We have had the dinghy covered until recently and everything was good. Left it uncovered for a couple of weeks during which it rained. There you go. At least that's my highly developed scientific theory. Oh, and mechanic said there was ethanol debris in the carb as well. Either PO was telling me a story or he got a load of bad gas from someone.