Richard Biddick, 76, of Baring Road, Croydon, Surrey, appeared at York Crown Court on Friday when he pleaded guilty to two charges of indecent assault on the pre-teen boy between December 1979 and October 1980.
Prosecuting barrister Jonathan Sharp said there was a degree of grooming in the offences to which Biddick pleaded guilty.
In addition to the Scarborough matters, Biddick has also been committed to York Crown for sentence on offences in Surrey, namely breaching a sex-offences prevention order and possessing indecent images of children.
Those matters were transferred from Croydon Crown Court to York, where Biddick will now be sentenced for all the offences.
Mr Recorder Harris adjourned sentence for a psychological report but told the disgraced pensioner: “Inevitably there is going to be a prison sentence of some length.”
Biddick was remanded in Hull Prison until sentence on April 8, when he will learn of his fate via live video link from a custody suite.