It was when a teenage boy entered a confessional booth to reveal the Catholic sin of masturbation that Melbourne priest Peter Waters started "grooming" him.

Father Waters, in his 30s at the time, was a talented piano player and writer, gregarious and charismatic, teaching one of his young charges how to drive and taking him on an overseas holiday.

As their "spiritual mentor", he befriended underage boys at the parishes he worked at - and their families too - including the child in the confessional.

Through the partition, Waters recognised the boy, addressed him by name, and asked about his sexual practices. The boy felt like he was encouraged to continue masturbating.

Prosecutor Robyn Harper said it was the 1980s when the boy stayed overnight with the priest.

The boy pretended to be asleep, she said, when Waters climbed into his bed and molested him.

A similar fate befell the boy's brother, who woke to Waters climbing in his bed after socialising together, consuming alcohol and cigarettes.

Formerly "best buddies", the brothers drifted apart under the weight of their secrets, only becoming close again now Waters will finally face justice.

The retiree, 74, faced a County Court plea hearing on Thursday, before he is sentenced for molesting the brothers and another three children in Melbourne parishes between 1974 and 1987.

A court-imposed gag order prevented any media reporting on two trials he faced this year, but it can now be revealed a jury last month found Waters guilty of six counts of indecent assault and one count of gross indecency with a child under 16.

The jury also acquitted him of four counts of indecent assault on a female and one count of carnal knowledge of a girl between 10 and 16.

On the morning his second trial was to begin, Waters confessed to one count of indecent assault of a male and two counts of indecent assault.

In a statement read to the court, one man described how Waters "swooped in" during his teen years while his parents were divorcing.

He said he'd return home after school to find his molester smoking and drinking coffee with his mum.

Another man's statement detailed how he suffered flashbacks after being molested by the man he once considered "my rock".

"He has no moral compass or sense of responsibility," he said.

Yet another victim spoke in court, saying even years later, he'd had trouble being intimate with his wife and had been terrified of also turning into an abuser.

Defence barrister Amelia Beech said Waters had been of good behaviour since the offending and "he still practices his faith".

Judge Scott Johns will sentence the sex offender on September 25.