Oh, good point, I never worked on a generator so I wasn't making the connection between engine RPM and output frequency. I'm familiar with UPS systems where the output power/frequency is completely decoupled from the input because the output stage uses sine wave generators. Since there are no electronics in the generator other than the electric motor and wiring, it makes sense the RPMs should be a multiple of the output frequency. Since I'm at 3750 now I may adjust it down to 3600. Or maybe I'll just figure out how to measure the output frequency. Or just leave it alone since it's only a few percent off. Thanks for the input!