Witnesses sought over unsolved Tas murder

It has been more than two years since Simon Crisp was shot dead outside a northwest Tasmanian pub and police need more information to solve the crime.

The 44-year old was shot three times as he put rubbish in bins outside the Marrawah Tavern after closing time on July 13, 2013.

Investigators at the time described a "premeditated and callous act", with the killer waiting in hiding before gunning down Mr Crisp, while his partner and her daughter were inside the pub.

Detective Acting Inspector Richard Chugg on Thursday said hundreds of people had been interviewed as part of the investigation and there was a $50,000 reward for information, but leads had dried up.

"We're asking those who know who murdered Mr Crisp or who know information that could help the investigation to reconsider their position," he said.

Police believe there are people who know what happened, but "for personal reasons" have felt unable to come forward.