McCauley is up to 6 years for recommended overhaul. Am thinking that
Hartzell is either 5 years or 6 years (more to follow). This is not
mandatory for 91 operations, but periodic internal inspection/reseal is
highly recommended.

Useta have a prop shop across the ramp that was a sister company. Never
really saw a lot of corrosion-related scrap out of the McCauley end,
but I would still recommend an internal inspection/reseal. Any
reputable prop shop could give you a quote. Pretty sure most of the
older McCauley designs have been retrofitted with oil-filled hubs. If
an option (and not already present) I would highly recommend it.

Most of the scrap from the Hartzell end hub-wise was corrosion related.
The hub bearing cavities of compact-hub Hartzell's weren't painted back
in the good old days. Am thinking that the 6 year calender interval
applies to compact hubs that have been painted internally.

Very little corrosion is permissible in the hub. If there is a little
corrosion present now, it may be repairable. If there is a lot present,
you probably don't want to be flying behind it. Again, a quote for an
internal inspection/reseal is common and relatively inexpensive,
depending on what they find.

The older steel-hub Hartzells are also susceptible to corrosion, as are
the blade clamps. It really isn't anything you want to screw around
with.

Hope this helps;

TC