Re: 1975 Evinrude Mate

[Don]

OK, well anything is possible, that is for sure….So, it is surely worth the minimal effort to remove the plastic air intake and try it that way…
It is also worth trying the carb from the other engine as well. Are you sure the carb air vent isn’t accidentally plugged with a screw….I remember an incident I had years ago in the shop with one of these engines, someone had rearranged some screws and plugged the carb vent. Usually, the carb will flood over when this happens though. The only other thing I can think of is the choke mechanism…Is the plastic choke knob detent in place and working OK? The choke will be able to flop around if the plastic detent is missing, which might explain the hunting symptoms.
You resused the original lower crankcase head/seal assembly, were you able to look at the lower seal in the process? The seal may be fine, hard to say.
Is the engine hard to start when cold, or warm? If the engine seems to start OK, this is often a good indicator that the powerhead is OK.