Had an interesting experience at the weekend so just looking for some pointers, advice and the usual useful suggestions that always come from Sailnetters
Anyway, I was motoring out of the harbour, normal cruising revs which on mine is about 2800rpm, had the main up as I was going to sailing shortly. There was a clunking, sounded definitely transmission related and I had something similar previously (which I thought I'd fixed but there you go). Throttled back and into neutral, I have an Edson single lever control, back into forward, throttled back up and all fine again.
About 30 seconds later, same clunking, this time when I throttled back the engine revs climbed, and climbed. Back into neutral and off she went, revs up and up. I pulled the kill lever, no effect.
Mildly concerned by a hundred pounds of pig iron trying to destroy itself under my feet, I went below to pull the access covers off to get her stopped. Of course there were a bunch of things in the way so it took me about 30 seconds (a guess, time has a strange way of deceiving you in these situations).
Just as I was pulling the first access cover off, the revs dropped back down as if the throttle had been closed, and then she shut off (same as she does normally, kill lever was pulled remember).
She had revved so hard that one of the water hoses was starting to come off. I tightened everything up, checked what I could see and there was nothing obvious causing it.
After mulling my options, changing my underpants and so on, I fired her back up again, took a few seconds longer than usual but she fired and sounded pretty normal. I motored back to my slip at just above idle.
Went back to the boat Sunday and took the engine control covers off, all looked spotless in there, everything seemed to work smoothly. Couldn't see anything obvious anywhere, only slight tickle was the dipstick touching the throttle lever on the engine when the throttle was open. Bent that out the way. Fired her up, let her warm for a few minutes, revved in neutral no problem, ran her for several minutes in forward at about 2k rpm (can't go any higher when tied up, the load makes her smoke like a chimney), same in reverse at 3k rpm, nothing untoward.
So.... any thoughts on a cause, how to prevent it in future, anything else I need to check etc?
Seems somehow different to most/all the other things I have read about a runaway diesel, she was running at full throttle for at least a minute or two I would think, but never got to the destructive part where bits of engine were flying off and puncturing my hull.
In hindsight, I wish I had checked the throttle was closed at the engine end because that would have at least told me it was an actual runaway, but that's hindsight for you.