I wonder if some kindly engineer might spend a few minutes advising about this subject.
It has to do with an auxiliary engine in a yacht, namely a 1 cylinder Yanmar. I believe that idling such an engine, for long periods, causes carboning of the injector and is consequently, to be avoided.
My wife-who does all the sea-going these days-rubbishes the idea.My mind harks back to days in convoy when, if there happened to be the odd motor-ship plodding along at 7 knots they might, on occasion, be given permission to break station for the engineers to open her up to get rid of some of the carbon blocking the injectors.
That exercise resulted in a mini display of clouds of sparks flying out the exhaust and talk of scavenge fires etc..
I did not find the right solution from the internet.