In Dutch, a "J" is pronounced like a "Y" - so Uanis is (kind of!) understandable!
His surname (Portfleet in English) is likely to be Poortvliet in Dutch?
I can see 4 births on WieWasWie.nl:
Johannes Poortvliet, 18th July 1834, 's-Gravenpolder municipality
Johannes van Poortvliet, 16th July 1838, Oud-Vossemeer
Johannes van Poortvliet, 26th August 1839, Oud-Vossemeer
Johannes van Poortvliet, 23rd September 1840, Oud-VossemeerAHA! Better fit is:
Johannis Cornelius Poortvliet, born 13th October 1836, Breskens
I searched from 1831 to 1841.
The 1836 birth shows:
Father - Simon Cornelis Poortvliet
Mother - Janna van Alten
Incidentally, I'm not too keen on how the registrar quoted his name at marriage?!

March qtr 1861
King's Lynn district vol 4b, page 595
Wardell, Martha
Poortohit, Johaimes Cornelius
Poorschit, Johanne Cornelius