Very true indeed, the only consideration being that the "machine shop" may be a work bench (or on a 46m Palmer Johnson or a 40m Sanlorenzo not even that!) and your tools may be a set of spanners, pliers, screwdrivers,... So what do we do with emergency repairs? MacGyver! I would love to have access to raw material and a lathe, a pillar drill, a welding machine and some other proper tools. But I don't! So we have to ask the local workshop to manufacture even the simplest things to great expense for the owner but still probably cheaper than setting up our own workshop. Even if you had the proper tools and spares not all manufacturers or insurance companies would allow you to touch the engine anyway. I think the most important part of your section quoted above is: and it of course here all the training and experience is put to test. Being an experienced marine engineer you would be more suited to foresee the events and come up with a strategy than someone with less sea-time and less sea-related education.