Stuart, I think the correct pronunciation is along the lines of Vertsilja, but most people say Wartsilla.
Jack, there are a huge variety of engine types around, the two main categories are 2 stroke / slow speed engines and 4 stroke / medium speed engines. Within these categories there are various manufacturers who all offer various models of engine aimed at different power output ranges.
In the medium speed market (mostly smaller ships and larger ships with multiple engines (cruise ships and ferries) the leader would be Wartsilla with MaK rapidly catching ground with their new M43 engine which has proved to be very reliable and very fuel efficient, although MAN / B&W and Deutz are still major players.
In the slow speed market there are only really two companies who matter and those are Sulzer (Wartsilla) and B&W.
When a ship is designed the naval architect will predict the power requirement to give the required service speed and then look at the engines available in that range, most engines can be purchased in various cylinder configurations (apparently MaK's come in an 8 cylinder version!) so that you can have a 6300kW MaK M43 (7 cylinder) or an 8100kW MaK M43 9 (cylinder) or pretty much any figure you like within the range.
