what is the birth date for George Powell and where was he born?

I know of 3 convict George Powell's who arrived around that time but none in 1837.
the first arrived on the Prince of Orange in 1821, settled in Woodlands, Hunter river. Then the Guildford in 1827 and settled in Patrick Plains. The Waterloo in 1833, lived in the Singleton area, this one didn't get his ticket of leave till 1841, sooo maybe this is your George
Yes a birth or death date would help or even a marriage.
There was a Thomas Powell who arrived on the Mangles in 1837 and a William on the John both settled in the Queanbeyan area but no George.

This is all the Geoge Powell registered on this site: http://www.slq.qld.gov.au/resources/family-history/info-guides/convicts

There are details for over 123 000 of the estimated 160 000 convicts transported to Australia. So if your George is not one of ones below he must be in the 37000 missing

Title: George Powell, one of 299 convicts transported on the Marion, 27 September 1847.
Details: Sentence details: Convicted at Gloucester, Gloucester Quarter Sessions for a term of 7 years on 24 March 1846. Exile.
Vessel: Marion.
Date of Departure: 27 September 1847.
Place of Arrival: Van Diemen's Land.

Title: George Powell, one of 214 convicts transported on the Waterloo, 11 March 1833.
Details: Sentence details: Convicted at Stafford Assizes for a term of life on 26 July 1832.
Vessel: Waterloo.
Date of Departure: 11 March 1833.
Place of Arrival: New South Wales.

Title: George Powell, one of 200 convicts transported on the Runnymede, 11 November 1839.
Details: Sentence details: Convicted at Southampton Town Quarter Sessions for a term of 7 years on 01 January 1838.
Vessel: Runnymede.
Date of Departure: 11 November 1839.
Place of Arrival: Van Diemen's Land.

Title: George Powell, one of 301 convicts transported on the Clara, 28 January 1864.
Details: Sentence details: Convicted at Hereford. General Quarter Sessions Hereford for a term of 6 years on 30 June 1862.
Vessel: Clara.
Date of Departure: 28 January 1864.
Place of Arrival: Western Australia.

Title: George Powell, one of 190 convicts transported on the Guildford, 22 March 1827.
Details: Sentence details: Convicted at Lincoln Assizes for a term of life on 08 July 1826.
Vessel: Guildford.
Date of Departure: 22 March 1827.
Place of Arrival: New South Wales.

Title: George Powell, one of 136 convicts transported on the Prince of Orange, 02 October 1820.
Details: Sentence details: Convicted at Berks. Assizes for a term of 7 years on 19 July 1819.
Vessel: Prince of Orange.
Date of Departure: 02 October 1820.
Place of Arrival: New South Wales.

Title: George Powell, one of 166 convicts transported on the William Glen Anderson, 31 May 1831.
Details: Sentence details: Convicted at Middlesex, Westminster Quarter Sessions for a term of 7 years on 03 December 1830.
Vessel: William Glen Anderson.
Date of Departure: 31 May 1831.
Place of Arrival: Van Diemen's Land.

Title: George Powell, one of 280 convicts transported on the Ramillies, 25 April 1854.
Details: Sentence details: Convicted at Devon. General Sessions Exeter for a term of 10 years on 05 September 1849. Ticket of Leave.
Vessel: Ramillies. [160 convicts disembarked at Gibraltar and another 157 embarked giving a complement of 277 convicts transported from Gibraltar to Western Australia]
Date of Departure: 25 April 1854.
Place of Arrival: Western Australia.

Title: George Powell, one of 188 convicts transported on the Atlas, 16 January 1816.
Alias(es): Bowcott
Details: Sentence details: Convicted at Radnor Great Sessions for a term of life on 31 July 1815.
Vessel: Atlas.
Date of Departure: 16 January 1816.
Place of Arrival: New South Wales.

England & Wales, Criminal Registers, 1791-1892
Name: George Powell
Age: 19
Estimated Birth Year: abt 1817
Date of Trial: 23 Jul 1836
Trial Year: 1836
Location of Trial: Sussex, England
Sentence: Transportation

States on Register, crime robbery, original sentence death, changed to Transportation for life. no ship given.

Is there a report of a death in custody in British BDM register? George Powell may have died from a disease in gaol or the hulk awaiting transportation to Australia.