I have a 1985 Johnson GT 150. It will run and idle roughly on hose muffs for a few minutes but will eventually cut out. It will start but not keep running in tank for more than a few seconds. I put new plugs. I have done as others have suggested in this forum and tested spark on all cylinders with a 7/16 gap spark tester and spark is good, however some cylinders will spark simply while turning key in ignition while others will not spark until engine actually starts to turn over. I don't know if this is normal or abnormal. I have tested compression and all cylinders are around 90 psi. I have loosened the gas cap that leads to fuel tank to test if vent line is possibly closed and got no difference in the engine performance. I have had someone keep squeezing the fuel bulb once engine starts to see if fuel pump might be issue but that doesn't keep engine running. I took carbs off and they looked very clean but I cleaned with carb cleaner and air compressor and put back on with new gaskets. The engine has new power packs, new stator, new spark plugs and wires. What should I do next to diagnose the problem? Would a bad impeller or water pump keep the engine from running? How can I determine if timing is ok if engine will not keep running? Any advice on how to proceed is greatly appreciated.