Hi Mayann The book " Ships of Our Ancestors" cites two ships by the name of NECKAR. Both belonged to the North German Lloyd line. The first one was built in 1874 and the most recent was 1910.
Regarding your grandmother's grave, several questions come to mind; have you checked with the cemetery office or the church? I had the same dilemma with my great grandfather. I called the church office and was able to at least get the date of death and where he was buried. Unfortunately he was buried in a paupers grave as he was only in the US for 6 months before he was killed in the coal mines of Pa.
I had a Mass for him instead . Maybe that would be an option for you too.