and the one I was flying that had just finished a 2000-hour overhaul had a MAP of 17...
Possible Causes
1. MP Guage error
2. Induction System Leak
3. Carb Icing
With a difference this big, I would definitely get it checked out! An induction leak could leave you without power just when you need it most.
The pre-takeoff MP checks are the only times you'll be able to spot this. In flight, the governor may mask any of the problems above.
You should know what to expect (and check for) MP guage indications at three pre-takeoff stages; before engine start; engine idle; engine operating ERPM with no load.
cl12pv2s