The Flynns wrote:
75% (that is 2700 rpm at 7500' or POH values)
I have a 62" Sensenich prop and a low time engine (170 SMOH by Mattituck)

Have you had your tach checked or calibrated recently?

I helped with the tach check at the AYA convention last
summer. We checked 3 dozen planes. Most were 100 rpm
(or more) low, with the tendency to be least accurate at
highest power settings.

Of course, your weight, temperature, and how the plane is
loaded are also factors. Suffice it to say while we loves
our Tigger, we don't see 138 kts TAS at 7500 ft. We are
usually traveling w/in 100 lbs of max gross and near-
rearward CG. 'Course it's not uncommon to be over 70 degrees
at 7000 ft here, either.

Cheers,
Sydney