Warrnambool Coast Guard flotilla deputy commander and skipper Keith Prest said the alarm was raised soon after 5pm when the fishermen's boat suffered propulsion issues.

He said the four men in their 20s had put in at the steep ramp at Boat Bay, about five kilometres west of Peterborough.

Mr Prest said their boat lost propulsion and they were being pushed towards the Peterborough cliffs by the swell.

As they were nearing the breakers and dangerous water, a small boat was able to pull them to safety and then a larger boat started towing them back towards Warrnambool.

They were met by the Warrnambool Coast Guard, who towed the fibreglass boat back to Warrnambool harbour.

"They lost power, there was a fair bit of a swell and Boat Bay is a very steep ramp, not for the faint-hearted," Mr Prest said.

"We took over the tow well past Childers Cove and got back to Warrnambool about 11pm.

"It was a good result all round. It was a bit tricky in the swell. Friends had brought the trailer down from Peterborough to pick up the broken down boat."

Mr Prest said the fishermen had two excellent sized tuna, probably about 80 kilograms each.

"So it wasn't all bad for the boys," he said.

"We had five people on our boat and it was a pitch black night. It was very tiring condition and we were completely reliant on our instruments," he said.

Earlier: A Good Samaritan has saved four men stuck at sea after the engine on their fibre glass boat blew near Peterborough on Sunday.

Koroit Acting Sergeant Lachlan Barr said the four men aged in their 20s were fishing off the Bay of Islands about 5pm.

"We were called to reports of the four males in a fibre glass boat that had a blown motor and was heading towards the rocks," he said.

"It was right on dark and Warrnambool Coast Guard was still about an hour away.

"Fortunately a good Samaritan has come by, hooked them onto his boat and started towing them back to get them around to where the coast guard could access them."

Warrnambool Coast Guard arrived about an hour later and transported the four men to Warrnambool's breakwater.

Acting Sergeant Barr said the "good Samaritan" was a man from Port Campbell.

"It was lucky he was there to help," he said.

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