The Angolan frontman has made one Barclays Premier League appearance for United, who let him spend part of last season on loan at Panathinaikos.
Hull have not yet secured a work permit for the 25-year-old but hope they will be able to achieve that before Saturday's match against Arsenal.
Tigers boss Phil Brown is optimistic Manucho will be a useful addition to his squad.
He said: "The lad is a proven goalscorer at certain levels, though not yet at Premier League level.
"He is 6ft 3in, 6ft 4in, great stature, he has a good eye for goal, and is certainly good aerially."