The ONLY engine you need to learn about is the one in YOUR boat. Basic diesel concepts are book learnin' applicable to all small diesels. Details of differences are critical. I have a Universal which is different than a Yanmar, raw water and fresh water cooled engines are different Hands-on? ONLY your engine is worth the time and $$
While I agree with the above, it also depends on what kind of sailing you are planning on doing. An example. We just got back recently from a sailing trip to Thailand with a couple of friends. The boat we chartered was a little light on maintenance to say the least. During our trip the water maker started out non functional, autopilot quit working, the aft head needed a new joker valve, the slipping windlass became a non functional windlass, and the headsail which had seen better days, started tearing.
We got the charter company to replace the joker valve and get the air lock out of the water maker partway through the trip (we did the initial diagnostics). They also diagnosed the autopilot (not fixable during our trip), and the windlass at least waited til the last day to quit. We rounded up some sailing tape from some other boats, and did a temporary patch ourselves with the charter company's permission, which held up. To drop the headsail I had to rerun all the lines on the starboad side to make more sense of the mess and get the lines uncrossed at the mast and run the genoa halyard back to the cockpit. That needed to be done first so we could get the sail down and back up in the winds at the anchorage.
While I know my boat by the back of my hand, it helps to have a good general knowledge applicable to any boat in this situation. It makes you better able to deal with the charter company, and possibly it can make the difference on whether your trip is a fantastic on (ours was even with the issues) and you make due, or you whine about the issues and have a miserable time.
