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