75 HP Mercury water pump issues after replacing impeller please help

"so i took a 1986 75 hp mercur

"so i took a 1986 75 hp mercury out for its maiden voyage today and got towed back to the dock after 15 minutes. the water stream shooting out the side was really weak. after getting home and checking to make sure the spit hose wasnt clogged i dropped the lower unit and replaced the impeller and all the gaskets except the bottom plate. (it was fine)the old impeller looked really good. when i put it all back together and started her up NO WATER CAME OUT THE SPIT HOLE??? what next? anybody no where i can get diagrams of an 1985/1986 75 hp mercury, is there a gasket that goes inside the top of the impeller housing? i took the lower unit back off and stuck the garden hose onto the tube the water pump housing conects to and water came streaming out of the side spit hole like crazy, so i guess there is no blockage in the hose or block... need help bad. anybody have this problem or can offer any advice?"

"when you replaced the pump yo

"when you replaced the pump you did slide it on the key that likes to fall out right. you can look up parts here,http://www.crowleymarine.com/parts.cfm"

"yup, the key is installed. th

"yup, the key is installed. this morning i took it apart again and found that the top impeller housing rubber insert from the old housing was still on the water tube and there was a new one in the top of the housing so the old one was compressing the new one and blocking the tube. i fired it up and water was shooting out nice. i took the boat out and again it ran fine for 15 minutes and then bogged down and the weak stream is back. it seems to run fine until it warms up, could this be a thermostat issue and not a water pump issue?"

Just take the thermostat out a

Just take the thermostat out and leave it out