1996 Johnson 150 Thermostat Cover Woes

[Zorn]

My first post here. When I attempted to unscrew the old plastic thermostat cover on my '96 Johnson 150 (Explorer 215), the top snapped off clean leaving the plastic threaded barrel section screwed in. Any idea how to remove or unscrew the remains of the plastic housing?  Any special tools? BTW, the other thermostat cover unscrewed without a hitch. Appreciate any suggestions/recommendations. Thank you. Zorn.

[Capt. Bob]

A couple 3 pics would help.

[Zorn]

This afternoon I used a small screwdriver and hammer to gingerly break away the imbedded plastic thermostat cover. The metal threads look ok I but need to clean them off.  I was thinking of acetone to help dissolve the remaining plastic and screwing in a bolt with the same thread pattern before installing the new thermostat. Does that sound reasonable? I also will vacuum out any debris. Appreciate any help. Zorn.

[Zorn]

Was able to clean threads and successfully install thermostat. Thanks.