My recollection (tho not infallible) of the other navajo on the beach incident was that the engine was delivering power, but the turbocharger had failed. The pilot shut it down without checking the MP. He could have managed to get back to the field if he had first checked MP and left it running.
I think he'd taken off 36, and as he turned to get back onto 11, with the engine shut down, he lost altitude to the point it was only ground effect that kept the aircraft airborne (actually water effect) and had only one course, straight ahead to the beach on the other side of the harbour. Fortunately for him he'd managed to get through enough of the turn that there was be ach in front of him, and not only sea/
The one thing I do recall accurately is that when offered assistance by the AFAP, even tho a non member, he told them (actually me, because I offered it) to shove it.
That incident was about 1981 or 82