A bit of a scare this weekend

[rwidman]

I had a starter do this on a Westerbeke diesel in my ex Navy Whaleboat. Heard the whine after starting, shut down the engine and the whining kept going. Put my hand on the starter and felt the hum. Rapped it lightly with a hammer, and it quit. Never done it again.

That's what we call "percussive maintenance".

 

[cappy208]

So how common is it for a boat's starter to turn on without human intervention and keep running?

This doesn't happen on it's own. When the OP started the engine this started.
It's a direct result of human pressing the starter button/ turning a key during the start cycle. Either the starter button fails by sticking ON, and keeps sending power to starter, or the solenoid has a closed short that keeps it engaged, or the bendix fails and sticks out and spins the starter to death. I have seen key starts on diesels that fail (fairly often) enough to warrant a push button start. Most professional installations have push button for this reason.


I had to tow a yanmar SF in years ago that had an exploded starter. The owner was lamenting they couldn't figure out what the 'new' noise was. Until it got really silent. The he got a tow home! The starter was blown off the bell housing by the force of it locking up after it melted the innards.

 

[GFC]

I had to tow a yanmar SF in years ago that had an exploded starter. The owner was lamenting they couldn't figure out what the 'new' noise was. Until it got really silent. The he got a tow home! The starter was blown off the bell housing by the force of it locking up after it melted the innards.

Now THAT would be downright scary. Fortunately my wife smelled something hot and that's when this whole thing started.

We probably will never know which came first, the chicken or the egg. In other words, did the starter run away and cause the other issues or did something else start the chain of events and cause the starter to runaway.

We can speculate till the cows come home but we probably never will know for certain.

By way of an update. We're now just waiting for a new helm panel to be built. Once that is done the trim tab gauges and a new digital Systems Monitor panel will be installed in it and we'll be finished. Well, except for the sea trial to make sure everything is working properly.