Raven came with a DV24, originally installed 1991. The only real problem I have had with the thing is that it leaked oil out of the main sump. This turned out to be a poorly installed line for draining the oil and although it took some time to track down the problem once we did so it was easily fixed.
We also had a problem with oil coming out the exhaust. It appears that this was caused by excess fuel not lubricating oil. I'm not a mechanical whizz OK , but somehow it was do with fuel pumping through the system on shutdown. It was solved by making sure we always kill donk with engine at idle. With our previous boat shutting down while engine was revving at over idling speed was not a problem. The Bukh apparently doesn't like it. (No I don't mean shutting down engine at 2500 revs. I'm talking about only a few hundred revs over idle.)
Previous boat had a Volvo Penta . Compared to the Volvo the Bukh is quieter but uses a lot more juice than the Volvo. At first this concerned me greatly until I realised that because it is comparatively quiet we use the thing a lot more than on PB.
The other thing I do like about the Bukh is that it's about as big (I think) as you can go and still hand start when necessary.
All in all no serious complaints although I'm told that a three cylinder would be quieter still. ??? To date parts have not been a problem but then Bukh have an official distributor in Oz. I'm told that parts are a problem in SE Asia or Pacific region. No problem in Europe.
"Those who do not observe the impulses of their own mind must of necessity be unhappy." Marcus Aurelius