[C320-list] Am I slow under power?

[Nathan Mauch]

I'm a pretty new C320 owner and I'm trying to figure out whether I have a tachometer issue or an throttle governor issue (3GM30F) on my '97 #453.   At full throttle, I make 5.3 knots in a dead calm, but my tach is only reading 2200 RPM, which I know is well below rated max.  However, I've seen my tach wander and I'm not convinced it's working properly.
My question is, is 5.3 knots about right for this boat (15X10 prop) at full throttle, or is my tach corret and I'm not geting full RPM out of the engine?  Reading through previous posts, it sounds like I should be getting at or close to hull speed?
Thanks,Nate,S/V Mistral