F90 SS prop? noise

Replaced aluminum prop with stainless ( same diameter & pitch). Now have intermittent knocking noise at low rpm only from neutral to drive and neutral to reverse. Everything OK at all other rpm's. Better performance all around- just concerned with this new noise. Is it caused by the added weight of the stainless?

[boats.net]

Yes the heavier prop will make a noise at idle. The noise wont hurt anything but it sounds bad.Unfortunately there isn't a big prop choice for the F90.