Thank you for bearing with me Glynn, I do appreciate your help as I sail
into unknown territories, it's been a bit of a hard slog today!!! Anc had defaulted David's DOB to 1795 because on the 1871 census he said he was 76 years of age. On spending some time today looking at the 1851 census where he was "missing" I found a David EVANS living in Aberporth with his wife and children, right age and says he was born in Aberporth as does the 32029 mariner but calls himself a Seaman not a Master Mariner however I do think this is our man 32029.
So it was back to the drawing board with a sinking feeling but luck was with me today
I spent more time looking at the 2 censuses I have him on and on the 1861 census on closer inspection he says he is 60!! So that meant I had to knock 5 years or so off his age and manually adjust the default age.
Another search on the Mariners register and I came up trumps!!! On the second page bottom right is his address and yes it's in the same street in Liverpool where his wife and family are in 1851.
So this is definitely my David EVANS, I'd love to find our more about the ships he sailed on and the interesting voyages he seems to have had. Any further information you can find from your sources would be fantastic!!!