Exhaust coming from open impellar housing

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

Not sure what you are talking about here but a totally dry impeller might smoke due to both a lack of lubrication and cooling from a lack of water. For clarity, what year boat and engine?

My apologies,

Its a 2005 21v launch 325 indmar assault engine.

I didn’t check the smell of the smoke to see if it was rubber, it seemed to me like a lot of it was bellowing out after the engine had shut off though.

Yes it will. All excess water and water from exhaust manifold is dumped downstream into the exhaust and exits the boat out exhaust.so if no water then exhaust will find its way to the impeller

Thank you guys, that gives me peace of mind. I was thinking the exhaust would have to try and pass the thermostat before escaping the impeller housing so I was wondering if mine was stuck open.

Thanks again!

-Johnny O.