I have an engine that took a prop strike (previous owner). The engine was completely disassembled to check the crank, case, etc for damage. It was reassembled with new parts, bearings, rings, etc., overhauled cylinders, and mags with fresh 500 hour inspection. The logbook entry says "0 SMOH Lower End." What else would be required to list this engine as simply "0 SMOH?" How should I track this in my log book?

  • 3
    $\begingroup$ Which regulations are you asking about? FAA, EASA, etc.? $\endgroup$
    – Lnafziger
    Jul 24, 2016 at 14:36
  • 1
    $\begingroup$ This is close to being a dupe of this question $\endgroup$
    – Pondlife
    Jul 25, 2016 at 12:30

2 Answers 2


"0 SMOH Lower End." means just what it says. The lower end was completely rebuilt but there wasn't a complete overhaul of the "top end". Some of the old top end parts must have been re-used without being overhauled.

I would suggest speaking to the person who did the overhaul to get more information on why the top end did not qualify for 0 SMOH as well.


It's probably not possible to get a caveat-free zero since major if any time has been logged since the log entry. You're tracking two numbers now:

  1. Time since bottom
  2. Time since top (if a top was done, maybe cyls have just been replaced as necessary...that's perfectly fine).

This really isn't a big deal, practically speaking, but entries like these would have me asking follow-up questions as a buyer only because it's unusual see a bottom OH without the top being done as well. That said, it's very common to see and engine topped at least once between overhauls which has the effect of staggering top and bottom times anyway!

Assuming that you're in the US and operating under pt91 the engine can be run on-condition for as long as it stays healthy. This could be 4,000hrs over 50yrs if you know how to manage your engine.

If you're dead set on having a "typical" 0 SMOH entry in the logs you'll likely have to have the whole engine overhauled again. Don't do that. A bottom with 500hrs is safer than a freshly overhauled engine anyway.

Was it a stationary strike or was the engine running? What kind of engine is it?

  • $\begingroup$ It was an engine running strike. It is a continental IO-550 $\endgroup$
    – Chuck M
    Jul 26, 2016 at 11:22

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