good maintenance=good engine, I like universal
Some additional thoughts to consider, especially since replacing an engine can run $5-10k.While shopping for a boat, ask to see the records of maintenance on the engine and how often and by whom it was maintained.There are lots of little things that make a difference on IF it will start when you need it beyond just routine maintenance.For example, using synthetic oil or at least the proper rated oil (many ARE NOT rated for Diesel engines), changing annually and using manufacture's oil & fuel & AIR filters instead of cheaper after-markets, valve adjustments at recommended intervals, adding appropriate additives whenever fueling-up (e.g. Biobor), changing the raw-water impellor at least ever other year, replacing the pencil zinc's in the engine/heat exchanger every year, etc.Also, ask when the anti-freeze was last changed. Diesel's run hotter, and old anti-freeze can spot-boil, causing cavitation and block problems. It should be done about every 2 years.Don't forget to ask about the tranmission. What direction do they leave it in during sailing (should almost never be in forward, reverse can be best on trannies), and how often has the fluid been changed.Also, pay attention to the engine temperature after it has been running for a bit (should be typically under 180 and if the engine doesn't have a heat exchanger, then under 160 -- the temp at which salt falls out of solution and clogs the engine).Also, if boats are winterized where you live, proper winterization procedures can make a huge difference, so if applicable, familiarize yourself with the proper approach and then ask the questions of how it was done.Also there are a few non-engine things that can adversely effect the reliablity of an engine.Examples are the condition & frequency of cleaning the raw-water strainer, checking the engine oil level at every start, replacing the starter (& glow plug) switches at 5-7 years, checking engine panel electrical connections, verifying proper water out of the exhaust at every start, checking/replacing the belt, adjusting the engine alignment (to prop), etc.BTW, my $.02 worth on which engine, I have a Universal M25XP in my 88 Catalina and absoutely love it. It might be slightly noiser than some, but has never failed to start (and it's 17 years old with about 500 hours).As mentioned it has an electric fuel pump which makes fuel filter changes very easy as it has a bypass for self-bleeding of the fuel lines. It does have a 'zinc' in the heat exchanger which should be changed at least once per year perhaps due to it being a marinized kubuto block, but well worth the reliabilty of the block (think about how many of their tractors you've seen). As it does have glow-plugs, a good battery does make a difference, but it ALSO has a decompression lever, just in case...By contrast, I have heard of lots of problems with Yanmar's, especially related to fuel issues, perhaps because of the lack of an electric fuel pump (as mentioned) or that they typically use larger micron filtering material in their fuel filters, allowing more junk to get to the engine.However, to their credit, they are often quieter, sometimes with less vibration, sometimes more fuel efficient, and may have fewer dis-similiar metals, sometimes eliminating the need for engine/exchanger zincs.Lastly, consider reviewing owners manuals of some of the typical engines you have encountered (most should be on the WWW), so you are familiar with what is suggested and can ask to see if it has been done.Below is a link to a diesel engine forum which might also help.Hope this helps...