Dan wrote:

Neither being a lawyer nor having seen one on TV I would wonder if
resetting an hour meter without putting an entry into the log would
equivalent a false entry.

I agree. When I put the temporary tach in, I noted the reading of the
previous tach and the current reading of the new one. Had an annual in
the interim, and the A&P computed the actual time based on the two tach
readings.

I know how many hours the temporary tach recorded, and plan on adding
that amount of time to the old tach before installation. Appropriate
log entries will be made, but I'd like to get back to reading the
aircraft total time directly rather than have to compute it for every
log entry.

I don't think I'm alone in that regard...if you look at the listings for
replacement mechanical tachs on the Aircraft Spruce page, you'll see
they can be set to whatever value at a slight additional charge.

Ron Wanttaja