As a skipper, owner or crew of anything that floats you will most likely become acting engineer at some point, so you're going to need at least some basic electrical, plumbing and mechanical skills. Thankfully, many faults at sea can be easily resolved if you know what you're doing, and you have the right tools.
Within the global maritime training framework - you can legally skipper vessels up to 24m with very little or no formal training in many countries and most of the courses that are available in the sub 24m sector focus more on vessel handling and navigation with very little time spent on the engineering side.
So if you go boating, learn the ropes, boat handling, learn about safety, learn about navigation, but also learn about the boats systems too, it's keeping you alive after all.
For everything else - there's MECO.