Likely candidates for runaway are the Pathfinders (V Dub Rabbit) Detroit Jimmies and some English Fords. Dilution of lube with fuel oil from injectors or the return lines into sump can be the the culprit. Dumping the PCV line into the air cleaner can have surprising effect when stuff goes bad too. Pulling the air shut down on a Jimmy will probably suck the gaskets out of the compressor but better than a drive plate through the hull . Fairbanks Morse made the 'rock crusher'
Our Jimmy was many years ago and I may be a bit foggy as to how the kill mechanism actually worked. I don't remember a fuel shut off valve, all I know was that it worked, from the wheel. As neutral was extremely hard to find on the Twin Disc clutch it was just easier to kill it once I was in.