Can somebody explain to me why the engines in this pic doesn't have a water pump on the front of the engine.
Thanks

They have crossovers that take the place of the circulating pump. The cooling system can be fed all the way through by the raw water pump and the circ pump is not needed on a raw water cooled boat. You can actually lower temps in high perf engines by removing the circ pump, and it takes a few horsepower to spin it at higher RPMS.

Are their any advantages of the circulating pump?

On an engine that is already set up with it (belts, hoses, etc.) it takes some work to convert over and on some engines it will raise water pressure so a regulator may be needed. Also you can't use a thermostat so getting good heat will require different restrictors in the system, takes some tweeking to get it right.