Post a picture of the primer solenoid valve and where the hoses off it go.----Seems to me those have to do with the primer.----Agreed not all these motor had the airbox.----I think it was left off of these starting in the early 1980's models !!!
The question is ----Does spark jump a gap of 7/16" on a test device.----Your answer as it stands is a no.----Sparkplugs are not used to test maximum ignition output !
On the 5.5 HP you have to remove the powerhead.----Simple job with 7 screws and a few hoses.----Allows you to inspect / replace o-ring and gasket on the mechanical seal on top of the driveshaft.----A good design and the shift mechanism never goes out of adjustment like many newer motors.
Does spark jump a gap of 7/16" on all 4 leads , yes or no.-----Stop trying to run this motor.----Find the problem.-----If a carburetor was plugged you would be starving one cylinder of gasoline and most important ----OIL----as well.----You could do serious damage.-
Post compression test numbers.----Maybe a plugged carburetor.------Maybe a ruptured diaphragm in the fuel pump.-----Sheared flywheel key.-----Should be easy to determine what the issue is.
Well----I machine my own sleeves for Mercury carbon steel driveshafts.----In fresh water I have never seen a pitting issue on driveshaft on Johnson / Evinrude motors.
