Bluebird's old engine was not strong enough to make it go this fast, so it was replaced with a more powerful Bristol Siddeley Orpheus engine taken from an old fighter jet. Many other changes were made, the tail fin from the fighter was attached to Bluebird's rear, the cover over the cockpit was changed to push through the air more easily, and the floats at the front were also changed. Bluebird was taken to Coniston Water to be tested in 1966. The tests did not go well, the weather was too bad to test the boat while moving, so it was tied down and tested without moving instead. When testing the engine it sucked in too much air and caused parts of the boat to break. The engine was broken when the broken parts were sucked into it. This meant that the entire engine had to be replaced.