The sinking of a fishing boat which left two crew members dead was "entirely preventable", an Adelaide coroner has been told.

Marine surveyor Adam Brancher said the 6.4m vessel had numerous problems and should not have been out at sea on the night of September 28, 2008.

He was giving evidence on Tuesday at the inquest into the deaths of Adam Mark Nicolai, 28, and his friend Justin Shane Hellyer, 28, off the coast of Stansbury on Yorke Peninsula.

The boat's owner, Andrew Pisani, managed to swim to shore.

Mr Brancher, who inspected the boat after it sank, listed numerous problems, saying "whatever margins of safety there were, they were so eroded as to be non-existent".

When the owner modified the boat, he should have presented the vessel to the Planning Department, which would have ordered repairs.

The sinking was "entirely preventable", he said.

Mr Pisani's lawyer Nick Swan referred to the owner's statements that the boat sank after it had been hit by two huge successive waves.

Mr Brancher agreed that if that had occurred, a number of his concerns about the boat would not have caused the sinking.

But he stressed the vessel should not have been out at sea in the condition it was in.

Mr Pisani is expected to give evidence later on Tuesday.