Whilst manipulating the scrotum with your mouth, shake your head back and forth making a "motorboat" engine sound.
It's the male version of the motorboat.
Last night, Janine was circumnaviagting my scrote and then she went crazy and scroterboated me. I may now marry her.
Verb: to motorboat someone's ball sac as though it were a woman's cleavage. Scrotorboating is not exclusive to the nuts, and can even include said activity on someone's taint.
"Please just go down on me. When you scrotorboat me, it tickles and I losefocus!"