Cavitation would be my first guess as far as why it matters. The 2nd would be the 'drumming' or vibration felt in the cockpit
or elsewhere. It gets annoying but more than that, at certain RPMs, it can be a problem. F'rinstnace, at high RPM
. Getting props synched is the key. I wouldn't say 300 is "a little off". Split throttles at the helm
is mildly annoying but could be a prob when close in for maneuvering. At that point is becomes one of the peccadillos of this damn boat.
Of course you've contacted engine mfg, right? What do they say? Have cat mfgs even gotten to the point of synching RPMs through syncrophaser?
EDIT: absent any other taletell symptoms could it be your tach gauges are off? What does fuel consumption
show? You do pay attention, right?