This is the wet end of the Emerson pump in my Jacuzzi spa. Pictured above is a broken freeze plug adapter. The freeze plug adapter threads into the pump (lower center of pic). It broke with part of the threaded end still in the pump. What is the best way to remove the part that remains in the pump? None of these parts are metal.
Drill a hole in it, then use a standard screw extractor. But a new plug and re-install. FYI, its not a freeze plug. It is used to let trapped air out of the pump before priming on initial fill/refill and startup.