Ben Jackson wrote:

My IO-540 with Hartzell compact 2 blade prop is smoother at 2700 RPM
than at cruise (2200-2400 RPM). If I have it dynamically balanced at
cruise will it vibrate more at climb power? Does the fact that it's
smooth at climb power suggest that the engine/prop combo is okay and
there is a problem elsewhere (mounts, etc)?

Prop balancing is done on the ground, with the engine running WOT at
whatever RPM is attainable during a static run. For most aircraft,
you cannot get the engine up to climb RPM during balancing.

Balancing is always a compromise, but doing the balance at
~2000-2200 rpm is better than not doing it at all.

If it cant be balanced, then all of the potential reasons are mucho
$$$.

Bent blade
Mistracked blades
One blade has bigger angle of incidence than the other
Bad motor mounts
Wrong prop/engine combination
Counter weights on crankshaft
Bent crank
....

MikeM