Runaway Engine: Anyone playing with... tinkering with a running outboard engine, opening the throttle butterflies by flipping the carburetor linkages in neutral... OR... running on a flushette and opening the throttle whether in neutral or in gear... you risk a "Runaway" engine scenario.
A runaway engine transforms itself from a ignition powered engine that depends on spark to ignite its fuel to a pure bred bonafide diesel with a never ending desire for the ultimate in rpms. Turning the key to OFF, yanking all the spark plug wires off, grounding out that well know black/yellow kill wire, does absolutely nothing... and that engine continues to scream away, grabbing at even higher rpms.
Yes, you could disrupt the fuel flow in some manner, then wait until the fuel lines, pump, and the carburetors to run dry while you're praying for the rods to stay put. That usually doesn't end well.
Now, if you happen to have the carburetor face plate off, and you're wearing a pretty heavy shirt of some kind... quickly ripping that off and jabbing it in the carburetor throats would flood the engine out fairly quickly, otherwise I'd suggest you run away... very fast, before that thing explodes like a large grenade. A better plan would be to not race the engine to its high rpms in the first place.
The above action works well, however, in this age of outboards, many have the carburetors separated... an assigned few to each bank, a good distance from each other... and you have but one shirt!
Your girlfriend's shirt?