1991 115 tlrp hard to start after warmed up

I have a problem with my motor that doesn't seem to be like any others that I have read about on this site, my motor will start & run great at an idle & has no problem running at WOT, I can back it down & idle around anywhere for any period of time, but when I shut the motor off to fish - for any extended period of time, the motor is hard to start (have to choke it). I have cleaned the carbs (3rd time was a charm), replaced fuel water seperator, replaced all fuel lines, cleaned the antisiphon valve, replaced impeller, replaced spark plugs, primer ball & the quick connect fitting on the motor. I have racked my brain on this one for a month now & have finally ventured to ask some pro's on this site. Does Yamaha use different fuel quick connects for each different model? I was going to purchase an oem connection, but the guy at the boat shop said that the Moeller fitting would fit all Yamahas. Could this fitting be the problem? Thanks in advance.