Generally using a small AC generator the generator shaft is direct coupled to the engine driving it. The frequency is a direct function of the rotational speed. The relationship is as follows:
P = 120*f/N where generator Frequency (f) = Number of revolutions per minute of the engine (N) * Number of magnetic poles (P) / 120 Conversely, P = 120*f/N. So for 60 Hz a two pole generator would be rotating at 3600 RPM and that same generator in 4 poles (like a small diesel engine) would be rotating at 1800 RPM. For our UK friends, 50 Hz would be 3,000 RPM and 1500 RPM respectively.
My best guess seeing your numbers is that if using a frequency counter to measure the frequency or a small DMM with a frequency function you are either seeing noise or triple triggering the counter. If the counter allows input amplitude ranging (like for example most Fluke hand held DMMs) try increasing the range. To see numbers like 180 Hz (60 * 3 the shaft rotation would have to be 10,000 plus RPM which I seriously doubt.
If you have an old AC powered 60 Hz wall clock (the type motor driven and not a digital clock) connect clock to generator and set it. Walk away for about an hour. How well did the clock keep time? Using a scope do as KISS suggest if the scope has the features. If not, connect scope ground to generator neutral as suggested.
Ron