John Parrish, 70, of Castle Gates, pleaded guilty at Manchester Crown Court to four charges of indecent assault after his victim came forward after more than 45 years.
The victim only reported the abuse - which happened nearly every week between 1966 and 1970 in Salford - in January 2015, when his grandson had asked to join the Scouts.
He told police he had been regularly abused by Parrish between the ages of seven and 11, and that he felt obliged to come forward in case Parrish was still alive and abusing children. Learning of his grandson’s interest in joining the Scouts also contributed to his decision to report his abuser.
Detective Constable Cathy Blain said: “I have nothing but praise for the man who so courageously came forward and reported the abuse.”
“Parrish abused his position of trust in the worst possible way and my only hope is that the prosecution brings some closure after the victim suffered in silence for more than 50 years.”