TD, thanks for your concern, but having seen others do a range of things from Nothing(TM) to Run-the-Engine-for-an-hour-in-the pen-in-gear, I thought it was a question worth asking. No stress here - just curious.
I know there might be slight differences between makes/models, but a Diesel is a Diesel and surely there are "best practices" everyone should know.
Where did you hear that? Are you referring to a raw water cooled diesel or a fresh water cooled diesel? Either way, whether the engine is running or not, there will be seawater sitting in the cooling passages. So running the engine won't change that.
Hypothetically speaking? Fresh water cooled. "The engine must be started and warmed up at least once every 14th day while the boat is in the water in order to prevent corrosion.
" - Volvo MD2010-MD2040 Instruction Book pg 12... or perhaps Volvo don't know what they're taking about?!?
...and I suspect is where RichH is coming from, although, to me, it seems it doesn't take an hour for the engine to be "warmed up". Even so, running an engine for ~1 hour every 2 weeks would mean minimum 26 hours/year on the engine. That's still well within the max hours between service intervals. Perhaps that's the "how long" answered then!
The trend thus far seems to be to take the boat out for a spin on a regular basis.. not always possible, but I guess that indicates "run under load". Would that mean that someone doing a circumnavigation, say, would be advised to run their engine in gear
whilst charging the batteries - or is an alternator or two now considered to be enough of a "load"??