Is the little clip installed correctly to the float valve and float? Is the bowl vent clear (mud daubers)? You mentioned the primer bulb–what’s with that? Have you converted it?
Once you figure out the carb flooding, your next item should be the ignition coils. Actually, that should have been #1. ALL 1957 Evinrudes have cracked coils, unless they have already been replaced. You are wasting your time until you do replace them.
