Embarked 200 men
Voyage 131 days
Surgeon's Journal - Yes
Previous vessel: Parkfield
arrived 1 September 1839
Next vessel: Gaillardon
arrived 22 October 1839
Captain John Gray
Surgeon Superintendent William McDowell
Follow the Irish Convict Ship Trail
Blenheim convicts and passengers identified in the Hunter Valley
sailed from London to Kingstown, Dublin where 200 male prisoners were received on board on the 8th May 1839.
The men came counties throughout Ireland and had been convicted of crimes such as larceny, burglary, receiving, stealing, manslaughter, coining, murder, assault, rape, abusing serjeant, desertion, arson, perjury, forging a Will and bigamy. Several were also convicted of white boy crimes.
The Guard consisted of 20 rank and file of the 51st regiment under Ensign and Adjutant McGregor and Ensign Kirby. 
Departure from Ireland
departed Dublin on 19 May 1839 and spoke the Parkfield
on 6th June.
Surgeon William McDowell
William McDowell kept a Medical Journal from 23 April 1839 to 8 October 1839
He reported all the men to have been in good health on embarkation however there was an outbreak of dysentery in July. The surgeon considered it due to the bad water they had on board which emitted a most offensive putrid effluvia, almost intolerable, and caused many bowel complaints
Cape of Good Hope
Fresh water and provisions were obtained at the Cape on 6th August, however it came too late and three prisoners died from dysentery -
James Maginness (died 2 August 1839),
Martin Graham (died 26 July 1839) and
Michael Farrelly (died 7 August 1839).
Later another convict James Benson also died after suffering tonsillitis.
Very bad weather was encountered on 4th September, one prisoner James Feeney a 26 year old labourer from Westmeath, became so frightened that he required treatment from the surgeon. 
Arrival at Port Jackson
arrived at Port Jackson on 27 September 1839. William Brophy was probably sent straight to the General Hospital on shore where he died on 2nd October 1839. The remaining prisoners were landed by 8th October 1839.
Convict James Cross died in the General Hospital on 3rd December 1839 and Daniel Keene died in the General Hospital Sydney 24th December 1839. 
Notes and Links
1). Blenheim convicts and passengers identified in the Hunter Valley
2).Convict ships bringing detachments of the 51st regiment included the Neptune
, William Jardine
, Bengal Merchant
, Lord Lyndoch
, Earl Grey
, Blenheim, Waverley
and the Middlesex
3). William McDowell
was employed as surgeon superintendent on the Harmony
in 1827 and the Diamond
4). Kingston Harbour Dublin
(Dun Laoghaire Harbour ) Engraved by T A Prior after a picture by Edward Duncan - Prints of Ireland.
5). Other convict ships experiencing bad weather during the voyage
. Sydney Gazette 20 August 1839
. State Archives NSW; Series: NRS 12189; Item: [X642]; Microfiche: 738
 Bateson, Charles Library of Australian History (1983). The convict ships, 1787-1868 (Australian ed). Library of Australian History, Sydney. pp354 - 355
 Journal of William McDowell on the voyage of t he Blenheim 23 April 1839 to 8 October 1839. Ancestry.com. UK, Royal Navy Medical Journals, 1817-1857 Original data: The National Archives. Kew, Richmond, Surrey