Bob glanced at a clock on the wall. From somewhere in the distance he could hear breakers churning soddenly against a reef.

Clackett, crouching low in the curve of the boat’s side, looked anxiously at Bob. He paid no attention to Clackett, but gave the fly wheel a sharp turn, and listened. It was marvelous how completely he was in touch with the engine.

“Did you strain the gasoline before you put it into the tank?” he demanded of Clackett.

“Always do that, Bob,” was the reply.

“The carburetter valve is clogged. Lay hold here.”

In ten minutes the valve was clear, the engine “turned over,” and the motor working properly. Bob switched the power into the propeller.

“All right, periscope room!” he called through a tube.

“Bully!” came back the voice of Gaines. “We were almost on the rocks. You’re the boy, Bob!”

“Send Dick Ferral down here,” ordered Bob curtly.