The following graphs show some MMO orbital parameters around Mercury.
The gravitational parameter of Mercury used for the calculations is 22031.868551400003 km3/s2 (it's the value used to integrate the JPL planetary and lunar ephemeris DE/LE440).
The data file for MMO is very noisy.
Here's an example obtained from
WebGeocalc that shows the orbital period.
We see many spikes. To eliminate those spikes, a particular decimation technique must be used for the eccentricity, orbital period and semi-major axis.