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A search of the subscription site Roots Ireland failed to find a baptismal record for a William Curley with father Peter. Likely their RC parish does not have records back to 1840. There were six Peter Curley records in the 1855 Griffiths Valuation head of household listing for Co. Galway. The one closest to the area around Lake Corrib would be a Peter Curley in Ower townland in Killannin civil parish. Of course, we don't know if your Peter was alive and leasing land in 1855.
I did not see a Peter Curley death record in the area around Ower.
There were two Curley families in Ower in the 1901 census.
You can add William Curley to our XO Chronicles site https://irelandxo.com/ireland-xo/history-and-genealogy/ancestor-database