Referring to the link and sync of the carburator opening at just the right moment of the timing. The throttle cable should be unhooked until that is achieved.
Not sure how that would make the carb want so much fuel but maybe.
Not sure without seeing more. Primer and intake could also be leaking.
I assume when your checking the syncing that the throttle cable is disconnected?
Sounds like carburetion.....air coming from somewhere. Spray something combustible around....could be timing though. Your idle circuit should not be spun out that far.
Did you rebuild the carbs with OEM parts?
Are the plastic carb parts warped?
Like tim says, the purple and white wire should be hot when you first turn the key and push it in. HOT WHEN YOU PUSH IN THE KEY. if it's not hooked up, problem solved.
https://maxrules.com/graphics/omc/wiring/25_35_82-83_elec-remote.jpg
Maybe this will help. Also, carb cleaner or I sometimes use vinegar. Welding tip cleaners are a must.
https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1975&hp=2&model=2R75D&manufacturer=Johnson§ion=CARBURETOR
