5000-5500 is factory reccomended, but theres a catch to it. They have found propping them to run on the low side all the time has lead to powerhead failures in the etecs, and making oil in the 4 strokes. They want you to prop them near the top of the RPM band now, or just a shade over when running light so as to always keep the engine above the minumum reccomended low RPM at WOT.