I guess," he murmured. "Well, they're
a trio pretty much alike. The farther off they are the better I like
it."

Tom once more gave his attention to his own boat. He was going at a
fair speed, but not the limit, and he counted on reaching home in about
a half hour. Suddenly, when he was just congratulating himself on the
smooth-running qualities of his motor, which had not missed an
explosion, the machinery stopped.

"Hello!" exclaimed the young inventor in some alarm. "What's up now?"

He quickly shut off the gasoline and went back to the motor. Now there
are so many things that may happen to a gasoline engine that it would
be difficult to name them all offhand, and Tom, who had not had very
much experience, was at a loss to find what had stopped his machinery.
He tried the spark and found that by touching the wire to the top of
the cylinder, when the proper connection was, made, that he had a hot,
"fat one." The compression seemed all right and the supply pipe from
the gasoline tank was in perfect order. Still the motor would not go.
No explosion resulted when he turned the flywheel over, not even when
he primed the cylinder by putting a little gasoline in through the
cocks on the cylinder heads.

"That's funny," he remarked to himself as he rested from his labors and
contemplated the "dead" motor. "First time it has gone back on me."
The boat was drifting down the lake, and, at the sound of another motor
craft approaching, Tom looked up. He saw the RED STREAK, containing
Andy Foger and his cronies. They had observed the young inventor's
plight.

"Want a tow?" sneered Andy.

"What'll you take for your second-hand boat that won't run?" asked Pete
Bailey.

"Better get out of the way or you might be run down," added Sam
Snedecker.

Tom was too angry and chagrined to reply, and the RED STREAK swept on.

"I'll make her go, if it takes all night!" declared Tom energetically.
Once more he tried to start the motor. It coughed and sighed, as if in
protest, but would not explode. Then Tom cried: "The spark plug!
That's where the trouble is, I'll wager. Why didn't I think of it
before?"

It was the work of but a minute to unscrew the spark plugs from the
tops of the cylinders. He found that both had such accumulations of
carbon on them that no spark could ever have reached the mixture of
gasoline and air.

"I'll put new ones in," he decided, for he carried a few spare plugs
for emergencies. Insi