Orbiting the Sun once every 87.969 Earth days.
But it completes three rotations about its axis for every two orbits. Thus ... the time needed for Mercury to rotate about its axis is (87.969)*2/3 days.
2011 Mercury Retrograde Dates:
Mer R Mar 30 2011 12:48 24°Ar21' R
Mer D Apr 23 2011 02:05 12°Ar54' D
Mer R Aug 2 2011 19:51 01°Vi12' R
Mer D Aug 26 2011 14:04 18°Le42' D
Mer R Nov 23 2011 23:20 20°Sg06' R
Mer D Dec 13 2011 17:43 03°Sg52' D