The 1837 edition dropped the repeated pronoun I after even, but this deletion seems to have been accidental. It was not marked by Joseph Smith in the printer’s manuscript. Moreover, the resulting phraseology means that even now modifies the verb remaineth, which really doesn’t make sense. The Book of Mormon text has two other instances of “I even I”:
This phraseology is fairly common in the King James Bible (with 19 occurrences there). Thus the repeated I will be restored in Mormon 8:3.
Summary: Restore the I after even in Mormon 8:3; the 1837 printer seems to have accidentally dropped it here.