The orders would ensure a steady revenue stream in the next 2-3 years.
The yard, is already building two tugs for the customer, Greatship (India) Ltd., a unit of the Great Eastern Shipping Company, which provides services to India's growing offshore oil and gas industry.
"We have got a repeat order for two anchor handling tugs from Greatship," Yapa said.
The order for the second two boats was signed at Friday's ceremony with Greatship managing director Ravi Sheth.
The two boats in the new contract, worth 35.5 million US dollars, are to be delivered in 2009. Keel laying for the first of these tugs is scheduled for December this year and the second in February next year.
Yapa said the tug launched on Friday was the biggest vessel built by the yard and also the first time a vessel was built in the dock.
Previous vessels had been smaller and built and launched from the yard's slipway.
The tugs are meant to supply offshore oil rigs with crew and provisions, handle rig anchor laying and also rig towing.
Greatship India now had orders to build vessels with yards in Norway, Singapore and Sri Lanka, Yapa said.
CDL has built a range of tug boats for both local and foreign customers. It has been building and maintaining tugs for the Sri Lanka Ports Authority in Colombo and other ports in the island.
The yard has just completed delivery of the third and last tug for A. A. Turki Corporation of Saudi Arabia.
CDL is a subsidiary of the Onomichi Dockyard Co. of Japan, which provides management and technical expertise to the yard.
The yard's profits have been growing in recent quarters because of a good order book, for both repair work and new buildings.
Colombo Dockyard reported a 50 percent increase in net profit for the first quarter ending March 31, 2007, largely owing to repair work.Net profit rose to 200 million rupees in 1 Q2007 from 133.6 million rupees in the same period last year while consolidated revenue increased to 1.98 billion rupees from 1.71 billion rupees.