A rapist former priest and teacher will serve more time behind bars for sexually abusing a boy under the guise of first aid during a summer camp.

Michael Aulsebrook, 63, a repeat pedophile offender, indecently assaulted the boy aged about 11 in the 1980s during the Catholic-run camp he managed in Victoria while a Salesian brother.

The victim had complained of chafing after going to the beach and then jumping on a trampoline, so Aulsebrook took him to a first aid office and locked the door.

He gave the boy Fanta and got him to take off his shorts before rubbing his legs, chest, stomach and genitals, complimenting the latter.

When the child protested and grabbed Aulsebrook's hand, the brother said it was alright and would fix things.

He repeatedly digitally penetrated the child, patted his head, and told him not to say anything about what "we" did before giving him lollies and chips.

Aulsebrook was jailed by Victoria's County Court on Monday for 20 months after pleading guilty to the indecent assault.

He was ordained as a priest a year or two after the abuse, which occurred in either 1985 or 1986.

But he left the Salesian order in the mid-2000s after other crimes came to light and has become isolated from the church and his family.

"You are of course the architect of your own misfortune," Judge Gavan Meredith told Aulsebrook.

"The fact that you were a member of a religious order and camp director meant that you occupied a position of trust and influence.

"The faithful expected you to foster and care for those in your charge, not place your own sexual needs above their welfare."

His holiday camp victim told the court Aulsebrook's abuse had damaged his relationships, including with his children, and he finds it hard to trust people.

"It made me question myself, my religion, my sexuality and a lot of the way I felt about me over the years," the man said in a statement to the court.

Aulsebrook is already in jail for crimes including the drugging rape of a 12-year-old boy in 1988 while a teacher at Sunbury's Salesian College, Rupertswood boarding school.

He's also admitted indecent assaults in 1987 and 1995, including against a young girl.

Judge Meredith accepted the former priest is remorseful and has reasonable prospects of rehabilitation.

Aulsebrook must spend another 22 months in jail before becoming eligible for parole.