How does that design accomodate axial shaft motion? Half the seal is attached to the shaft, which is attached to the engine, which (if on rubber mounts) moves forward with power. If it moves forward enough, the seal faces separate, and...
Why the two hose barbs? Carbon/graphite is OK, but what grade is the stainless? Personally, I'd prefer a high-nickel stellite as the mating face.