No, I think the ratings are fine, I am thinking the pumps may have difficulty purging air when restricted and this is causing noise, either that or some of the US versions of the 1073.09 have some problem with either a broken shaft or bearing and I need to figure it out, the pumps should be quiet. Also, having tried to use one pump to run a skimmer and return I would say don't do it, it is a constant game of balancing valves that gets old very quickly.