We are planning to purchase a 1969 172 that a friend has owned for years. He bought it in the 90s and painted it, redid the radio stack, and the engine had a field overhaul at 1900 tt in 1997.

The plane then sat for most of the last 20 years, accumulating about 40 hours since then. It has been in annual about a dozen times it that span. The price is fair, considering the plane is very nice but will likely (possibly) need an overhaul in the near future. In looking thru the logs, I can't seem to find any paperwork/tags on the overhaul other than the entry in the engine logbook.

If the cam manages to hold together and we don't need to overhaul the engine, How much do the missing tags affect the value. We will likely sell the plane in 5 or so years, after my teenage kids have used it to get their licenses.

Any words of wisdom? Until we started looking for a 172, I had no idea how difficult a nice one is to find!

I would pull a cylinder as soon as you get it home. If the lifters are toast (like my 0320) and you catch it quick enough you can just do an Iran on the engine. If you run it and trash the crank it gets expensive quick.

Yellow tags are nice to have but not required.

Without yellow tags or some invoice/work order showing what services were performed or what new/reconditioned parts were used in the overhaul, how do you know the quality of the overhaul? I think this is true for a field overhaul to an even greater extent. If a name like Mattituck or Central Cylinder or something was attached to the work, it can probably ride on reputation alone, but for Joe Bob A&P, I'd want to see the documentation.

But then...if it's a very old overhaul, it should prob be considered in need of an overhaul soon. Like they say, sitting does the damage.

On a fixed pitch prop, for example, a yellow tag is timeless. On a variable pitch, an old (or missing)yellow tag does not improve the value at all. In this case, consider the type of parts that would have tags and what time/corrosion/wear could do to them - and assume the worst.

pilot wrote:On a fixed pitch prop, for example, a yellow tag is timeless. On a variable pitch, an old (or missing)yellow tag does not improve the value at all. In this case, consider the type of parts that would have tags and what time/corrosion/wear could do to them - and assume the worst.

That depends on the location. In Canada I would say a yellow tag definitely can increase value on a CS prop. When you have to overhaul it every 10 years, proof that it was done 2 years ago vs no proof is a $4000 difference...
As far as engine components go on a very old overhaul? I'm not sure they make a huge difference anymore, other than what Zzz said. But it'll likely need work anyways.

I was thinking along the same lines, with the 21 years that have passed it may be a non issue. Chances are there will engine work in the future.
Thanks for the replies!

I recently installed a TCM factory reman and it didn’t come with a single yellow tag. Log book entry only. How old is that case, crank, gears? Who knows. No AD record either.
Well the only yellow tag was the test run record.
A few local builders will give you a book with build photos, lot numbers and tags for even misc hardware for engine overhaul records. That can be very handy if some AD comes out against internal parts.