The man is accused of nine offences of indecent assault against children and eight of committing acts of indecency against children between 1973 and 1986.
He has denied all the charges and the court heard he told police he would be too embarrassed to expose himself in public due to having an "unusually small penis".
"The prosecution say this defendant is an entrenched paedophile. It would appear that he cannot help exposing himself to young people or getting himself into situations where he can sexually touch or assault them." said Sean Brunton, prosecuting at Plymouth Crown Court.