The victim was riding as a passenger on vessel #2 with his son as the operator.  The victim's daughter was the operator of vessel #1 who was following behind vessel #2.  Vessel #2 slowed down and vessel #1 could not stop in time to avoid a collision with V#2.  Vessel #1 then hit the victim in the back after the collision, knocking him off the vessel into the propulsion as it stopped.  

operator1 was an inexperienced operator with less than 20 hours of boating time.
Gerrish Twp                   