NameHeinrich Schreffler 
Children Names notes for Heinrich Schreffler
On 26 May 1765, at St. Michael’s Lutheran Church in Germantown, Henrich Schrefler and wife Anna Maria baptized two children: Johann Carl born 17 Nov 1764 and Johann Godfriedt 17 May 1762.
The “Internet” seems to believe this is Carl/Charles Schreffler who later married Magdalena Mertz.
Find-a-Grave notes for Heinrich Schreffler
His find-a-grave memorial suggests two possibilities for when he came to America.
Apparently there was a Heinrich Schreffler on-board the St Andrew Galley in 1737. Or, they suggest, perhaps it was the J Schreffler on-board the Ranier in 1749.
John Henry Mertz, founder of the Rockland Township Mertz family, and absolutely unrelated in any way to the Longswamp Township Mertz family was also on-board the St Andrew Galley in 1737. I think that is nothing but an irrelevant coincidence.
In my opinion, if everything else we think we know about Heinrich and his family is true, I would lean to the 1749 arrival (or even later). Heinrich baptized two sons in Germantown in 1765 and Germantown was a jumping off point form may Germans who came to America but they typically didn’t stay there long before moving out to the “hinterlands”.