Pressurized steam cleaner?

[packrat]

At work we use a c02 tank all the time {in remote locations away from the big compressors}
with regulator to blow of electric moters and starters out.
I got my c02 regulator from a Coke service man, free
But you do need access to c02 tanks and have a pressure regulator.

 

[Gedeon Spilett]

the small steam cleaner you mention gives ample steam output for a little engine, and for a larger one too, 50psi as you mention is quite enough.
a little wobbler well made would run by blowing with the mouth...

 

[Swordmaker15]

Update: We used a bicycle foot pump for safety. My boy took third place overall in the science fair. We had a blast and the other kids were fascinated with how the motor worked.