Thanks for information extra260bum .. 10,000 did sound too good to be true .. even on a pipe ..
I will assume that the 7850 was on the muffler that came with the engine ??
That works out to about 13 pounds of thrust at my altitude ( 650 feet ASL ) .. not bad for a can muffler ..

I'm still looking for a small gas engine for a Funtana 100X ..
So far the MVVS 26 cc with a pipe seems to be the only one that will provide 15 or so pounds of thrust ..
( I was trying to find a way around the tuned pipe but there really doesn't appear to be one other than going to a larger engine .. and even more weight .. )