Exhaust coming from open impellar housing

[Mushy B]

Hey everyone,

Did some research but would like some clarity.

Upon replacing the impeller I bump started the engine with the cover off the impeller housing to see if it would help loosen up the impeller and i accidentally started the engine.

I found that exhaust smoke was coming out of the impeller housing.

I know the exhaust and the cooling system are connected but should the exhaust be able to find its way back to the impeller on a cold engine with a dry start?

Is this indicative of the thermostat being stuck open?

Thanks in advance.

-Johnny O