Bill,
I found a Heinrich "Magrose" (misinterpreted Mayrose) on ancestry who was born in 1847 andtravelled from Bremen to Baltimore in 1865 and which noted that he was from Damme.
I have never seen a German surname Lehonkuhl and believe it is likely the surname Lehmkuhl.
Thus, I would encourage you to look in the Damme catholic church records for your ancestor. Whilethe emigration database is a wonderful aid, it is not a complete list and thus, one should still searchthe local church records. R.K. is the German abbreviation for roman catholic.
The Damme catholic church records are digitized and able to be viewed at your nearest Family History Center.
Good Luck,
Bob Behnen