FWIW

[Just Say N2O]

I also have a Mercury 90 SportJet in a Bayliner Reflexx, which is the second one I have owned. My brother also has one.<br /><br />On my current one, I just purchased the boat, I installed a gauge that is combination Tachometer and hour meter from Teleflex. I also installed a tach on my prior boat, as well as my brothers.<br /><br />On each of these, WOT rpm was between 5,050 and 5,200 rpms. I only mention this, because your WOT rpm of 4,750 seems low. If this is not because of Tachometer inaccuracy, it might idicate that even what you considered "normal" WOT, might have some issues.