Back again: It occurred to me- I have another problem that your thread might help me with... Have a Shindaiwa EB630 blower with an invisible crack in the bottom of the gas tank. Tried everything to patch it (vs a new one around 25 bucks). JBWeld worked for awhile. Do you think the Permatex Aviation would work? Cheaper than a new tank. Anytime i'm working with plastics i'm careful to make sure they're degreased. Can't get to the crack from the inside.....
And! still farting around with the Mantis. Runs like a scalded dog wide open for ten minutes now but-poof- quits. Just like before but longer.
I've done this to repair plastic outboard gas tanks, and maybe it'll work on yours if you want to give it a try.
After washing tank with warm soapy water I also spray some degreaser on area to be repaired. In my case I use brake cleaner.
Get/borrow a small soldering iron (like used for circuit boards) and when it's hot, trace the crack with it. On the red plastic tanks it will melt and re-fuse the plastic. Once you see the plastic starting to melt keep it moving. You can't stay on one spot for more then a second or two.
Once you think you've got it, put 5 to 10# of air to the tank and put a little soapy water on repair. If it bubbles, dry it and re-touch the spot. If you don't see bubbles your good to go.
I always try to trim a few shavings from the inside edge of filler, and will melt them into the crack as I go.
I've repaired several outboard tanks and put 20# of air in them, and they will hold it until I release the pressure.
Check YouTube, there's probably some examples there.