Well, that last line with "Mary still go lightly" isn't working for me; it conjures up discordant images from Breakfast at Tiffany's, which may well have been Jon Campbell's intention. What I'm trying now for both the last verse and the chorus is:

Chorus:
D7---------------------C----------------------G
In my mind I see her, steaming round the bend,
-----D7-----------------------------------C--------------------D
Her bow cuts through the water, her journey knows no end;
----G-----------------C--G-------------------------D--G
She plows on down the river, at the closing of the day,
--------------C-----------------------------------D------------------D7
And may the Mary find safe harbor, as she glides across the bay.

My apologies to Jon for deciding to do his song straight.

Cheerily,
Charley Noble