Sir James McKechnie was born in Oban in 1856. He received his early education at private schools, and was apprenticed to the firm of Messrs. Duncan Stewart and Company, Glasgow, when he was fifteen, wher hee worked in the fitting and pattern shops and in the drawing office. At the same time he attended classes at the Mechanics Institute, now known as the Royal Technical College, Glasgow. After further experience with other firms in the construction of engines for Clyde steamers and Atlantic liners, in 1889 he was appointed manager of the engineering works of Martinez-Rivas-Palmer of Bilbao, where he remained for six years. He was responsible for the construction and equipment of engineering shops and the training of native workers to enable the machinery of three Spanish cruisers to be produced in Spain. He was afterwards awarded the Spanish Grand Cross of the Order of Isabel la Catolia for these services. His valuable experience in naval design and construction was also sought for in connexion with ships for the Japanese, Russian, Turkish, and South American Governments.

After six years in Spain, McKechnie returned to the UK to become engineering manager at the Naval Construction Works at Barrow-in-Furness. He was responsible for the design of the machinery of the 22-5-knot cruiser Powerful, as well as for similar equipment for the Niobe and Amphitrite, all of which were distinguished for their good steaming performance and low coal consumption. In 1899 he was appointed a special director of the firm. Shortly after the outbreak of the first world war, he was made the managing director of the Naval Construction Works at Barrow-in-Furness, with full charge of the engineering and administrative sides, where, under his direction, naval vessels, from battleships to submarines and all types of naval armament and projectiles, also airship construction, was carried out.

McKechnie was also responsible to the Ministry of Munitions for the erection and management of projectile and filling factories at Lancaster and Morecambe. He was a director of several other engineering companies allied to the Vickers concern.

McKechnie was appointed a Knight Commander of the Order of the British Empire for his war services in 1918. He also held the Japanese Order of the Rising Sun. He was elected a member of the Institution of Civil Engineers in 1913, the Institution of Mechanical Engineers in 1901, and was also a member of the Institution of Naval Architects.

McKechnie died in London in 1931.