I bought them from a trucking company that upgraded the fleet.
They are from on-board APUs.
The APU housings and the condenser coils were trashed from rust and corrosion, so they are pretty much worthless for their intended use, but I think I can get 1 or 2 usable systems out of the bunch.
Beyond that, these little engines would be ideal for such things as Pete mentioned, or use them for generators. since they'll push 4,000 Watts.
I played with this one and it will idle down.
They are set at max throttle as-is.
I think I can re-position the throttle lever to gain some more RPMs, since max RPMs is around 2,000, wide open.
Mark.