if I over prime the Carb. itself it will leak foul from throat of the Carb.
I think your carburetor is different than the one Johnson equiped their 10hp motors with in 1953, but maybe it is similar enough for the following to apply.
On my 1953 Johnson Model QD-14, after priming with the primer on the pressure tank, when I prime the motor’s carburetor by pushing in on its portside knob, fuel gets propelled into the carburetor “throat” but will leak out the front if the motor is trimmed too high. I find that by tilting the motor back so that the primed fuel will flow towards the crankcase and not out the front, I can get the motor to start. If you’re using a test tank and stand setup that are not connected, then just put some bricks or wood blocks under the front of the stand to tilt it if you want to leave the motor’s tilt adjustment set for optimal display on a stand. Just be careful of the balence. Hope this helps!
P.S. I can see several photos you posted, just not in your post that said
Here are a few photos of the carburetor my motor has if this helps.
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