No water coming out of thru hulls

[roosterlfd]

I cleaned and fired up my boat today on muffs and found that there was not any water coming out of the thru the hull exhaust. Any ideas as to why this would happen? I removed the thermostat, thinking that I should probably replace it anyway, put it back together without the thermostat and tried it again. Still no water out of the thru the hulls. Any help would be greatly appreciated.