I think I replied to something like this a while back... Yes, it's a waste of time and money. The only real time you hear the rattle from the pump is while out of the water, during flushing. The rattle is caused by the pump shaft moving axially, back and forth, bouncing off the thrust bearing and washer. There is no thrust created on the pump, causing the movement. When the ski/boat is in the water, the torque, or pressure created by the impeller, pushes the shaft hard against the thrust bearing and washer, eleminating the noise. So, the anti-rattle kit is actually for nothing more than keeping you happy, eleminating the noise while back-flushing. Problem is, it really doesn't work; when they do, it's not for too long.