This series of centrifugal self-priming pumps closed coupled with HONDA (GP160) Air cooled 4-stroke OHV petrol engine has the characterizes to have the prime made by means of the emulsion air-liquid. The air of the suction piping is sucked inside the pump body the depression created by the rotating impeller, therefore it emulsifies with the liquid contains into the pump body. The emulsion air-liquid is pushed into the delivery channel where the air, which is lighter, gets separated and gets out from the delivery piping. The liquid, which is heavier, returns into circulation. Once the pump gets rid of all the air from the suction piping, the pump starts and it works as normal centrifugal pump, therefore the pump can work also with the mixture of air-liquid. There is a non-return valve fitted to the discharge side which enables a small quantity of liquid to be retained in the pump body thus allowing an automatic prime and suction lift to any application. This eliminants the need to prime the pump at each start up.