Read the logs carefully!
I'm in the midst of an (unexpected) overhaul on my Mooney. The O-360 had about 6100 TT, and 1200 SMOH. It was a first airplane so there was a LOT we didn't know to look for in the logs. It had been through 2 overhauls. A few things to look for:
- Has the crankcase ever been re-machined? You can have this done about twice before there isn't enough metal left. Figure 3k roughly for a new case on the O-360 (we didn't need one)
- Has the crankshaft ever been reground? Same deal here- you can only do this so many times before you need a new crank. The limit on the O-360 I think is 0.010" undersized. In our case, we were at the limit, and fortunately the journals were OK, and it didn't need a re-grind this time. Never really priced a new crank, but I think they are 3-5k as well.
We got away with a few close ones, but this is the last run on this engine for sure.
These are the two main components any overhaul shop will put in their 'disclaimer' when quoting, and this can blow the price way up. If you have to replace both, in my opinion, you are better off buying new.
Certainly there are other things to look for, but if the engine logs say anything about these two operations being done, I'd investigate further...and hopefully if they were done, the log entries were made. I'd feel better if you could also confirm with the shop that did the last OH, and there as a paper trail on what was and was not done.
I'm not saying to NOT buy the enine if these have been done, just know what you're getting in to.
Good luck...my engine turned out to be Pandora's box...not to mention all of the accessories & prop. $25k later, here I sit, reading about engines instead of operating one (another 3 weeks to go, if I'm lucky).
