skeptic

I would show up unannounced one morning and have the airplane towed out of his hangar to another location on the field while you are present. Take all the parts with you (rent a truck if necessary). Then arrange for another mechanic to get the airplane in condition for a ferry flight. I would not let anyone on the field know about your plans until you show up that morning to "reclaim" the airplane.

It is a pretty hostile environment above FL180. If you have a problem with your O2 system you will need to descend immediately, regardless of the weather or terrain below. My personal opinion is that there is not much reason to cruise above FL180 in an M20K unless you are taking advantage of a spectacular tailwind, or trying to top some really uncomfortable weather. Just make sure that you are willing to descend back down into that weather in an emergency.

I recently discussed this with a 231 owner. His airplane has GAMI's, intercooler, Merlyn, and LB engine. He said that in the mid teens he gets about 165 KTAS at 9.7 gph LOP. This is with CHT's all in the mid 300's or lower, and TIT well within limits. At lower altitudes he said speed was slightly less, around 160 KTAS if LOP.

Thanks for posting this picture.....very helpful.

If this is corrosion, can it be treated at this early stage with something like ACF-50 or similar?

The aircraft is blue on the outside. That probably does explain the blue "patch" inside.

Not sure, but I think that light surface corrosion can be treated with ACF-50 or similar chemical applications.

Not sure....looks kind of "powdery" in the picture. I also just noticed that part of the lower aft bulhead is blue, and opposed to the green primer color. I wonder how that happened?

The attached pic was taken inside an M20 aft fuselage. Does the light colored area on the aft upper skins look like surface corrosion? It was not evident with the flashlight, but the camera flash is of course much brighter.

It would need to be checked by a mechanic, but I doubt that the vertical free play exceeded Maxwell's limit of 3/16".

Which part in the trim linkage normally has to be replaced?

I just found a reference to this in an M20J service manual......max vertical free play at the rudder is 0.08 inches for a 201. Not sure if the 231 has the same limits.

I recently looked at a nice Mooney 231, and I noticed that when pushing up on the rudder and/or horizontal stab, there was some slight vertical "free play" around the the tail hinge points. Not the elevator hinges, but rather the hinge that allows the entire tail to move for trim purposes. Is this small amount of free play normal, or does it perhaps indicate some worn bearings? The airplane in question was in above average condition, and appeared to be very well maintained, so I feel sure that this would have been addressed if the owners had been told that it was a problem. It was obvious that they had not knowingly cut any corners on maintenance.

As follow up to my original post, I have since observed this condition on other Mooneys. The following picture was taken of a 231 lower right wing panel:

Thanks for the good comments. Always nice to hear from those that have owned and/or flown with these systems.