At times, Indian Navy officers are reluctant when it comes to using Indian manufactured equipment over those which are made abroad, former Defence Minister Manohar Parrikar said on Tuesday.Parrikar also said that there was immense potential for Indian businesses to manufacture equipment for the Indian Navy, while speaking at a seminar 'Indian Maritime Environment & Capability Requirement' organised by Confederation of Indian Industry in Panaji."What is required actually is determination and equally important is naval officers having confidence in Indian industry and Indian technicians. I found many times they were reluctant," Parrikar said."Each (imported) product which the Navy uses, has so many parts... The opportunity to convert them to 'Make in India' is tremendous," the Goa Chief Minister also said.Parrikar said that opportunities for private manufacture in the defence sector were so vast that they cannot even be thought of, citing the case of sonobuoys -- used in anti-submarine warfare."When I went flying on P-8I from east coast to Andaman, I realised that the quantity of sonobuoys is so high, that three four units can survive in India if we can develop technical collaboration on the issue," he said.He however pointed out that the one factor which deterred businesses from defence equipment manufacturing was that the only buyer in the segment was the Defence Ministry."Obviously, one disadvantage with defence is that the only consumer and customer is one. In other markets you have multiple customers, if you fail to get a business from one customer, he can go to the next customer. Defence is such an entity, where all your requirement is supposed to be supplied only by Defence," he said, adding that the policy of Indigenously Designed and Developed and Manufactured (IDDM) product in India, if pushed forward can be a great help for 'Make in India'.Parrikar also called industries to collaborate with the Indian Navy for commercial production.