"A regular mystery!" declared Jock. "Have that plug out again, Desmond old son."
Four times Findlay repeated the tests. The current easily ignited the dope in the plug when the latter was laid on the cylinder, but, as soon as the plug was replaced the petrol squirted, but it remained unfired.
"The clearance between the points is all right," he remarked, speaking to himself rather than to his companions.
For about half a minute he toyed seemingly aimlessly with the plug; then in an excited whisper he continued:
"I've got it, lads. At least, I think I have. Hand over that small spanner, Hayes. Thanks. Now bring our dinghy alongside. We'll try this little lad."
Very softly, so as not to disturb the occupants of the cabin (Findlay meant to give them a surprise), the outboard motor was clamped to the dinghy's transom. For the umpteenth time the engine was doped, and with bated breath Desmond and Hayes watched Jock grip the fly-wheel. One vigorous swing and the trick was done! With a series of rapid explosions the engine fired. Ahead shot the dinghy, the sudden acceleration capsizing Desmond and Hayes and throwing them in a heap upon the thwarts, while Findlay had only sufficient time to grasp the tiller and steer the dinghy clear of the yacht's side.
The roar of the motor brought Mr. Sadler and the Scoutmaster on deck. They were just in time to see Hayes and the Patrol Leader sorting themselves out, while Findlay, with a grin of triumph on his face, was steering the dinghy round the Spindrift at a speed that she had never before attained.
"By Jove!" exclaimed Sadler in sheer amazement. "However did they manage the trick?" Scoutmaster Graham smiled.
"You repent of your bargain, George?" he asked.
"Frankly, yes," was the reply. "Now that the old engine is letting out so nicely I rather regret my rashness. But a bargain's a bargain. Your lads have carried out their part, and I'll carry out mine."