When the shaft had been put in place, a coupling was attached to the end, and this in turn bolted to a similar coupling on the engine.
“Pretty good work,” commented Jim. “Now we’ll screw on the propeller; and then back to the water it goes.”
The gasoline tank was installed; then the batteries, spark coil, spark plugs and carburetor; and their work now required only testing.
“Bully job,” declared Jack, enthusiastically.
“Know how the engine works?” asked Jim, stopping to wipe a very grimy face.
“Sure thing, Jim,” laughed Jack. “This way: a mixture of gasoline vapor and air is drawn into the cylinder from the carburetor; the spark plug ignites it, and the piston is forced downward.”
“It’s a number of explosions, one after another,” put in Fred Winter, solemnly.
“The only thing I know about it is this,” said Joe, with a grin; “when the engine makes a noise, it’s going; and when it doesn’t, it’s stopped.”
“Why doesn’t it explode straight ahead?” asked Aleck.
Jim Benton laughed heartily.