A search for two men missing in waters off South Australia’s Eyre Peninsula has covered more than 100,000 square kilometres but has failed to find them or their boat.

Tony Higgins and Derek Robinson were on the timber-hulled Margrel, which left Coffin Bay on Thursday bound for Goolwa.

They made contact with a friend on Friday and reported having engine trouble, saying they were diverting to Kangaroo Island.

But no further contact was made, prompting police to begin an air search with the assistance of the Royal Australian Air Force.

The police Water Operations Unit joined the search on Tuesday, along with police aircraft and planes from the Australian Maritime Safety Authority.

Police said a total of 103,707 square kilometres had been checked without success.

The search area has even been extended to waters to the east and south of Kangaroo Island.