As David has alluded Kiki has a Yanmar it is a 4LHA STP 240HP.
http://www.quantumboats.com/downloads/4LHA-INBOARD.pdf
This are reputed to be amongst Yanmar's best engines quiet, economic and reliable a Google search will come up with plenty of information. I would not describe this engine as sounding like a London Taxi but then if you are used to Petrol
I am pretty sure the engine is based on a Toyota block as per fitted to the Land Cruiser; the 6BY is based on BMW and there have been some issues with this one.
Ours has almost 400 hours on and has never had any issue (touching wood as I write this). They are relatively easy to work on as they are not fly by wire, parts are readily available.
If you are interested I have a full workshop manual in PDF form if you want to look in more detail - PM me if you need it