"never have trusted the blooming things"
Every time my wife wanted to set an alarm clock, she asked me to set my quartz watch alarm "as backup." She said she didn't know how to set the watch alarm herself. So, I spent an afternoon going from shop to shop looking at travel alarms, and bought her the simplest and most foolproof one I could find. Every time she has used it, she has awakened before the alarm has gone off and shut off the alarm. She's never heard it ring for real. And, I still have to set the watch alarm as back up. I've told her to please let the alarm sound, because having it actually go "ding, ding" is what will build trust. But she won't.
So, you won't trust your engine until you use it, use it, and use it again. So, use it. Learn how to make it work. An inboard diesel is much better than an OB when you are trying to get upwind in a seaway. It might be important to be able to do that sometime.
Aside from dirty fuel, the most common diesel problem is a battery without the juice to start it. A $75 (maybe less) solar panel can help with that. The most common way to damage a diesel is to let it overheat, so the cooling system is vital.
the last one - fell off the no longer made mounts, blew a hole in the no longer made water valve, wore out the cutlass gland, got stuck in forwards gear, got the diesel bug, and twice I got it caught up in fisherman's debris
the outboards have never yet gone wrong....
I am sure I will come to love it for its fuel frugality, for the electrical power it produces and the dry heat the much bragged about bite
I will not like it for the way it will restrict where I can sail because of lobster pot fear, the ever present gentle odour of diesel, the size of the tool kit it demands, its lack of portability.
As for outboards - in all the years I have been running them I have never yet had a problem of any sort at all.... ever