as i was comming thru cleveland harbor about 2800 rpm's nice and smooth, i all of a sudden slowed down and my motor reved up over 4000 rpm's. i pulled back into neutral. i waited a few seconds wondering what had just happened, i then put it into gead (forward) and cruised to the ramps without anything further happening. i thought i might of spun the prop, but back on land i put the motor into gear and tried to turn the motor by hand. i didn't see it slip so i figure it is fine. anyone have any ideas what caused that to happen??? thanks for replys/opinions.