Johnson 3 cyl 70 hp, 1986. No vacuum at one carburator

[racerone]

The fuel pump runs on PRESSURE pulses from the lower of the 3 crankcases.-----If there are no pressure pulses the fuel pump does not work..-----That is not a breather line.-----It simply pull any fuel spillage into the engine.----A safety feature you might say.

 

[Bernt]

The fuel pump runs on PRESSURE pulses from the lower of the 3 crankcases.-----If there are no pressure pulses the fuel pump does not work..-----That is not a breather line.-----It simply pull any fuel spillage into the engine.----A safety feature you might say.

Thanks. I have the pulses, pump works fine. So even if that fuel pump pulse connector to the crankcase would be fully open to the atmosphere, it would not affect vacuum for carbs. Same for the fuel spillage line, correct? Desperately seeking easy fixes to my problem .

 

[racerone]

If the pulse line to the pump was fully OPEN you would have issues with air getting pulled in through the BOTTOM carburetor.

 

[racerone]

If the pump works fine then you must have crankcase pressure developing.-----Strange that you would have no vacuum.-----There is a possibility that the cylinder sleeve has rotated.-----Instead of jumping up and down around the boat pulling your hair out, pull the cylinder head.----Inspect cylinders and sleeve position .----Head gaskets are cheaper than a persistent head ache.