The man, who cannot be named as that would identify the victim, pleaded guilty in the Warrnambool County Court on Thursday to incest and two counts of indecent assault.

The offending occured at farming properties in two south-west towns between 1976 and 1983.

The court heard the man touched the victim's breasts and on one occasion sexually penetrated her.

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In her victim impact statement, the victim said she "grew up disgusted and confused with myself".

She said the offending caused a "dark hole, nightmares" and a "lack of trust and timidness in new relationships that was extremely overwhelming".

"The guilt, disgust and shame was so paralysing and I didn't know any better or different," she wrote in the statement read to the court.

"I refuse to be a victim any longer.... For the first time in my life I feel powerful," she said. "I say goodbye to your control. I am a survivor."

Lawyer Jarrod Williams told the court the offending was "unquestionably very serious".

But he said decades had passed since the offending and since that time his client had not engaged in any further criminality.

He referred to a psychologist report which stated the man suffered from "disinhibition".

Judge Michael McInerney will sentence the man on November 18.

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