I have an o.s. 160 with perry pump: today I noticed that the fuel line from the tank to the pump is full of fuel and bubble free while the fuel line from the pump to the engine has a lot of bubbles and if I spin the propeller by hand the bubbles seems to start from the pump. Do I need a new one? needles to say that the engine runs very bad and even if it don't stop it seems that it wants to die and after that it keep running

Sounds as though the diaphragm is bad in the pump and they are not repairable