Clive Richardson was holding a knife during the first encounter with the boy and also wore a nappy, Teesside Crown Court heard.
Prosecutor Rupert Doswell said Richardson had the victim wash him in an intimate area and also forced the boy’s hand onto his groin.
He then told him not to tell anyone about what had happened.
Richardson then carried out a similar attack a few weeks later while he and the boy were again wearing nappies.
The abuse, which occurred in County Durham, dated back a number of years, but only came to light in March 2014 when the complainant contacted police and Richardson was arrested.
He denied indecent assault and gross indecency, but was convicted by a jury after a trial.
In a statement, the victim said he despised Richardson and had become “Mr Angry”, using drugs to block out memories of the abuse.
He had also suffered from depression and had suicidal thoughts.
Richardson, 39, of Eastway, Scarborough, who uses a wheelchair because of a problem with his leg, was of previous good character and had made a positive impact on society, said Felicity Hemlin, mitigating.
She said in December 2010 he helped save a man’s life when he fell into icy waters. She also said his age at the time of the offending was a significant mitigating factor.
Judge Tony Briggs said it was just possible to suspend a jail sentence on Richardson.
He received a 21 month jail sentence, suspended for two years and a supervision order. He will have to register as a sex offender and be subject to a sexual harm prevention order for the next seven years.