1972 Johnson 25rl72r rebuild

I’ve picked up a 25hp for my boat and it ran good enough but as I dig into it. It stopped pumping water, it does not like to idle for long either. Cleaned the carb and tested in bucket was doing good. Took it out for a run and ran great out to the lake center shut it off fired right up and road back to shore. Second trip is when it began stall out at idle. But ran good otherwise. Took the carb off cleaned it real well checked and double checked everything set back to factory and fired it up in my bucket to start getting the fine tune and no water was spitting. Checked impeller, housing, plate. Doesn’t make any sense why It wouldn’t pump. Pickup tube is good can push water through up and seams to come out the spit hole in back. Where do I check next? Plan is put the lower unit on and to pull the thermostat off to see how far the water is getting maybe a clog?

Pulled thermostat and nothing is getting up to it. Tried to prime it by pouring water down into it with the muffs on and running, still nothing? Pulled the lower unit off pushed water through the water pickup and it seems to come out the spit tube as well as the exhaust? but doesn’t make it up to the the thermostat??? Is there a water jacket or something between the pickup and the motor in the exhaust housing? Put a drill on the lower unit shaft and sitting in a bucket it will pump water up the tube so that’s ruled out.

Maybe you didn't get the Tube inserted in the Pump Grommet when you reinstalled the Gearcase

The grommet on the pump housing is a little dry but I pulled the power head off and the gasket was blown out. And melted plastic? Is part of the gasket made of plastic under the motor?