Man injured in Sydney as boat hits tinny

Four people in a motor boat have allegedly hit and run a man in a fishing tinny at a Sydney beach.

Police say they are looking for two men and two women who took off in a 20-foot, cream-coloured motor boat near Balmoral about 2.30pm on Sunday.

A 47-year-old man had been fishing in his tinny near Middle Head, when the boat allegedly took off and crashed into the smaller boat.

The man suffered back injuries after he was knocked off the tinny and was helped to shore by people on nearby sailing boats.

He was taken to Royal North Shore Hospital with injuries, including cuts and bruising.

Police say they want to speak to the four people who they believe were on board the motor boat when it crashed.

The man's damaged tinny has been taken to Balmoral Beach where it will be forensically examined.