I started to fog my cylinders on my 1999 Mercury 135. When I started to remove the plug on top left hand cylinder, I realized it was some loose, not to the point you could lift it out by hand but it would not tighten up or be removed without a socket.  I have noticed a large increase in fuel consumption and planned on doing a compression test later, but now with this loose plug issue I sure am some concerned. The plug seemed dark as if "rich" fouled. Any ideas on what o check and consider? Sure appreciate some ideas, thanks

i had a f-150  strip the threads and launch a plug out of the head. (aluminum head vs. steel plugs, plug wins) a mechanic friend of mine installed a helicoil type devise. he drilled the hole out, put a special fitting in, it was spiked on the outside and threaded for a plug on the inside. then he drove a special punch in it, it drove the spikes into the block. put a plug in,truck never missed a beat.

Well thanks, I will check that out. I dunno how it could have stripped, but next time at the lake I will look and see, thanks