Smelly Motorboat 

The Smelly Motorboat is the less recommended alternative to motorboat. You simply place your face inbetween the well endowed ass cheeks of the he or she and shake your head rapidly side to side while yelling, thus causing the sound effect of a motorboat... although a smelly one.

Guy 1: dude my girlfriend has no rack
Guy 2; looks like your gonna have to go for a Smelly Motorboat

Smelly Motorboat by Jarlus December 9, 2008