The sailboat in question is a 1980 37' Hunter Cutter. Unfortunately the way that the engine is designed, it comes with a mechanically triggered compression release, which triggers at the end of the throttle swing. I haven't gotten too far into the way that its set up, as I've been working on getting the wheels in motion to get the major repairs started first.
And as far as the engine not having an actual stop device, this isn't that completely abnormal on older diesel engines. I remember my father having a Kubota tractor some number of years ago, and in order to shut that diesel off you had to physically pull a lever that shut off the fuel flow until the engine sputtered and died. So i never thought twice about having the same setup on my boat.
In reply to the question about the bang noise, imagine if you will, a steel connection of some sort, say a dirtbike chain we're to snap at the coupler, and then, under load, the pieces of the linkage slamming into another metal object. I imagine the connector on the end of the shift linkage failed (new cables last year though...?) and because of some sort of mechanical bind forced the connector off the lever and jammed the keeper pin into the chain drive on the steering wheel. I mean i know that's a pretty fantastic theory, but at least to me, this whole chain of events seems like it was one of those "one of a kind" events where everything fails at once.
And Edison is the pedestal manufacturer.