How a Mechanic shocked a ship captain?

A giant ship engine failed. The ship's owners tried one expert after another, but none of them could figure but how to fix the engine.Then they brought in an old man who had been fixing ships since he was a young. He carried a large bag of tools with him, and when he arrived, he immediately went to work. He inspected the engine very carefully, top to bottom. Two of the ship's owners were there, watching this man, hoping he would know what to do....