Hi ,I have a problem with my BMC 1.5, I have just replaced my old engine with a rebuilt BMC 1.5,on returning from the boat yard back to my moorings the engine was lightly revving up and down,once back at the mooring we checked all pipes for leakage which there is none so we have bled the engine roughly about 6 times,it settle down for a while ticking over ok,but now it revs high then just cuts out,we had the fuel tank fitted around 8 years ago it is only a 30 ltr tank,which is all we need,would it be possible that this has some crud in the tank,which is causing the problem or is it anything else that we can check,regards.