9/21/2015 Did test of RD-15A seal. Rotated shaft with socket wrench manually. Spark plugs removed and the air connection to the intake was plugged with a short length of hose with a drill inserted. I had wiped off the top of the motor and the seal cavity then added the oil. I also removed and checked the carbon and square ring and put them back before the test. All solid and good. The crankshaft bearing is tight and rolls smoothly. 
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Used blue Walmart TCW3oil and noticed small bubbles at forward end of the seal. I saw the bubbles when the shaft key is generally to port as in the picture above. Looked like they probably were from the vertical drain slot. To check I removed the seal spring and bottom washer and left the carbon seal in place. 
Rotating the crank shows big bubbles come out of the vertical slot when the crankshaft key is in the position shown in the first photo.
During the test oil was constantly draining down so I had to keep adding. I looked throough the carb throat at the end of the test and saw blue oil drip on the face of the reed valve plate so things were draining normally
It looks like air from the crankcase pushes oil out of the vertical drain slot, at least when the engine is not running. I can see no way to fix this and I have a 1954 Evinrude with the same symptom – oil all over the top of the engine and getting into the mag plate. The 1955 and up engines use a conventional seal. Did the factory recognize this problem? Is that why the redesign? Could I remove the carbon seal and then use a seal for a 1955 engine?
Thank you.