MAYBE IT’S NOT A MISSING PROP?
If your boat doesn’t respond to a bit of throttle, don’t assume the prop’s missing. Similar symptoms can be caused by a cable linkage problem, a broken shear pin, a ‘stripped’ key in the prop/shaft, a sheared flexible coupling or even a gearbox failure.
Isolating the problem is easy: open the engine cover, start the engine and have someone put the engine into gear while observing the engine and drive mechanism.
Assuming all is in order, you’ll need to check the prop. An outboard or sternleg can be tilted up, but with any sort of shaft drive you’ll have to jump into the water to physically check out the prop.
If the prop’s still on the shaft but not turning when the engine is in gear (or only turning slowly) the problem is likely the shear pin or key (the piece that sits in a slot between the shaft and prop hub).
With outboards, it’s possible that the rubber hub inside the prop is damaged (it’s designed to protect the engine and gearbox if you hit something solid). In either of these cases removing the prop and replacing the sheared item is a relatively easy fix.