850 Carter Thermoquad flooding at low rpm

So it was running fine and then it started blubbering ?
I would go with looking at basics as described here carefully,
before u spend $ having it rebuilt
After about a hour it started getting noticeable, tach fluctuating periodically, at the 2 hr mark it almost died at a stop. Ran extremely rough, sputtering until I got it over 2000 rpm for a period of time and started running better, a couple of hard acceleration’s it started running fine again.