Bermuda-registered Arethusa (Offshore) Ltd. would have suffered a loss of $1.5 million in its third quarter, but the sale of a mobile offshore drilling rig resulted in a profit of more than $26 million.

The offshore oil company said it earned $26.4 million or $1.30 per share, compared to $546,000 or three cents per share in the three months ending June 30.

The profit came as a result of the $27.9 million sale in June of the Treasure Stawinner , which offset the loss , caused by the need for repairs to one of the company's rigs.

Quarterly revenues from contract drilling revenue increased to $32.3 million over $29.2 million for the same period last year.

"Our quarterly results were negatively impacted by unanticipated downtime and repairs to the Arethusa Scotian after leg cracks were detected during a routine underwater inspection,'' said Arethusa president and CEO Mr. Jan Rask.

Mr. Rask said by the end of 1995, seven rigs, over half the company's fleet, will have incurred downtime for enhancements.

"With further upgrades scheduled to occur during the fourth quarter, Arethusa has sacrificed utilisation and earnings during fiscal 1995 to enhance our fleet capabilities,'' Mr. Rask said.

"As a result of these upgrades, with higher demand for deep water drilling units, we have been able to position the company for significantly improved results and reduced downside exposure during fiscal 1996,'' he added.

The company said lost revenues and repairs totalled about $1.7 million during the quarter and the rig has now returned to work in the Dutch sector of the North Sea.

For the nine months to June 30, total profits were $21.5 million or $1.06 cents per share compared to $3.2 million or 16 cents per share for the same period a year earlier.

Had the company not sold the Treasure Stawinner , the nine month results would have a loss of $6.4 million or 32 cents per share.

Revenues for the nine months were $87.7 million compared to $90.3 million for the same period a year ago.

Arethusa owns and operates 13 mobile offshore drilling rigs in the Gulf of Mexico, Brazil, Egypt, Holland, India and Indonesia.

Assets increased to $372.5 million at June 30 from $347.8 million at September 30, 1994.