I wanted to point out that the recording of the name "Mary" as "Marah" is looking as not unusal for the times.
I have been surfing Genealogy.com and the NEHGS site all day and have found it twice while looking at families.I will transcribe one entry:
"Mary, born January 16, 1669/70; married Samuel Mott, of Lyme, April 6, 1692, and they had a gift of land from her father, March 27, 1697; her name on the Town record is written Marah, that being the form which town clerk, Joseph Peck was in the habit of useing for Mary"
Mary was Mary Brockway, daughter of Wolston Brockway.
So your Marah is more then likely not a mispelling of Mary, or an error in transcribing, but was an actual entry for the name Mary.