My Oberdorfer replacement for the original Sherwood seems to be running good after 100 hours. However, when I checked the impeller, I noticed some abnormal wear in the face plate. I held a steel straight edge against the plate and noticed it was not flat, but had about a .005 inch bow to it- applying more pressure to the impeller core area than the fin area, hence creating some moderate wear on the face plate in that area. (The bow was facing into the pump). The area where the fins rotate showed very little wear. I will grind and polish the plate flat on both sides and place it back on the pump. It seemed that the engine ran about 5-10 degrees warmer with the Oberdorfer. I'm wondering if I was loosing some suction/efficiency from the bowed face plate. I will update later in the season after launch. Thought I would mention this...others might want to check plate flatness when changing impellers, or if they notice temperature changes between the two pumps.