Is it a taam or a rio aqua pump? Some are known to be noisy others quiet down and stay quiet. Make sure the seals look good, I have heard of horror stories of them having sels fail and put copper into the water.
"The other big problem with the skimmer is that it comes with a low quality, noisy RIO pump as a default. Even the manufacturer of the Remora admits that the RIO has starting problems. When starting, on occasion it will make a 'clunk clunk clunk' noise and refuse to start. I replaced my pump with a Maxijet and I'm happier."