I took my old stainless battered prop off and after removing I noticed a roughly 2.5" dia X .5" thick chunk of what appeared to be black rubber that had melted?
You will have to pull the exhaust elbow and replace the shutter. It sets in the top of the exhaust tube. You will also have to find out what elses is melted and find out why you had the overheat that caused it to melt.
Thanks, my father in law had the motor rebuilt years ago and it may have been left behind. I will pull this and check. Is there a good write up on this around?