A locked, fenced-off compound at the North Otago Yacht and Power Boat Club in Waterfront Rd, lined by three rows of barbed wire around its top, was believed to have been entered on Friday night or Saturday morning.
Club commodore Kevin Murdoch said it was likely fuel was targeted during the break-in.
Those responsible appeared to have gained access from the rear of the compound, he said.
"One of our members went down and found out their boat had been interfered with. There were eight boats that had covers slashed and I suspect they were looking for petrol. Nothing we can see at this stage has been taken.''
A hydraulic line to an outboard motor on one boat was also cut. He believed the offender or offenders had mistaken it for a fuel line.
It is the second time the compound, that holds about 25 boats at any given time, has been targeted. An outboard motor was stolen several weeks ago.
The club planned to install security cameras to deter future break-ins, in addition to a camera mounted on the club's building.
He said boat owners took security seriously, but advised them to be extra vigilant.
"What we say is not leave things like fuel and batteries in boats; anything that can be easily taken.''
That extended to the likes of fishing rods and life jackets, he said.
Sergeant Blair Corlet, of Oamaru, said the matter had been reported to police and CCTV footage from the area would be analysed.
Inquiries are continuing.
