“Monkey yourself!” retorted the lad who had been acting as engineer. “All I did was to screw the spark plug in a bit tighter, and shut the pet-cock.”

“Then you probably cracked the porcelain on the spark plug, and there’s a short circuit,” spoke Frank. “Here, let me take a look, and see what the trouble is,” and as Frank had been successful in times past, when the others had failed, they made room for him at the motor.

He looked it over a moment, and then, seeing that the switch was on, gave the flywheel a couple of turns. There was only an apologetic wheeze.

“He knows so much about motors,” sarcastically murmured Tom to Ruth.

“He knows enough to turn on the gasoline, at any rate, and not try to run the motor with what’s in the carburetor,” snapped back Frank, as he opened the cock in the pipe leading from the tank in the bow. “Who started this motor, anyhow?”

“I did,” confessed Tom, the tables thus being turned against him.

“Next time turn on the gas,” repeated Frank. “It’s one of the first things to do in running a motor-boat, sonny. You may write the word gasoline twenty-five times before you go to sleep to-night,” and all joined in the laugh against poor Tom.

“Huh! I supposed it was always kept turned on,” he said in defense.

“The carburetor leaks a little, so I always shut the gas off at the tank,” explained Sid. “I guess I forgot to mention it.”

“And I can easily guess why,” spoke Frank, with a significant glance at the pretty girl beside whom his chum was sitting.