[myates92]

Take a chisel and give it some straight down taps (not trying to loosen) just straight perpendicular force to the bolt head face. They make a tool called an impact screwdriver, try to cut a slot in the bolt for the screwdriver to bite. Try heating the case and not the bolt itself. Check to see if the bolt is magnetic or not, could be aluminum or stainless (not magnetic). Some stainless bolt plating reacts with other metals and can seize if heated or left to the elements. If it’s to far gone, keep in mind what you have to loose... no shame in asking for help. Pull the motor take it to a machine shop.

PS. One last thing, if it won’t hurt anything internally or if it’s not a blind hole, try drilling all the way through the bolt... that will typically relieve some pressure of binding on the threads... then try taking an easy out to it.