The tool in question turned out to be a 11/16 socket and matching crescent wrench. A bit hard to see in the picture but I finally succeeded in loosening the bolts on the shaft coupling- which is the flange attaching the propeller shaft to the engine. I’ll get more into the why I spent 4.5 hrs (1.125 hrs/bolt) lying on my back crammed into the crawl space underneath the cockpit in a later post. For now it is enough that the thing is done.
Wanted: Mechanically Inclined Yoga Instructors