Typical power settings during cruise and other phases of flight

One concept you should understand is full throttle is only full power
at sealevel. As you climb, your manifold pressure guage will indicate a
lower reading. Also, you will not be able to obtain full power.
However, the air gets thinner, so you don't need full power to go as
fast a True Airpeed (TAS). A typical setting is somewhere around 24"
manifold pressure and 2400 on the tach. If you have a flight manual for
the plane look in it and pick one of those settings.

Also, remember that as the air gets thinner, you need less fuel. That
is why you need to lean the mixture as you climb.