I've seen some amassing things welded up with these little 140 amp welders I have a Hobart 140 myself but hardly ever use it for anything but body work or welding on stuff less than 18/" thick mostly because I have several larger welders better suited for the thicker structures, and can get the job done in less time.
My worry about the smaller machines is they can not achieve the penetration depth of a higher amperage machine.
That being said there was one time when the only machine I had at my disposal to do a repair with was another guy's 140 and what I had to weld was well over 1/2" thick the weld was 6" long. I preheated and pre heated till I was blue ion the face then proceed to run several passes of .030" gas-less wire. It took forever and I had to keep heating almost all the time but in the end everything held together just fine. Sometimes we do what we have to do.