Good Morning Boaters, I just got a 1972 Johnson 50 hp. I got is started and after about 5 minutes of running on muffs the alarm went off. I replaced the water pump the same way that it was installed. Started it again, the alarm went off. I pulled the lower unit again and realized I put the impeller in backwards orientation. I flipped it around and reinstalled it and tried again. Now I got some water coming out of the lower unit pee hole. but after a while the water quit flowing and the alarm went off. I have now replaced the thermostat and tried again. No water came out. Alarm went off. I have pulled the lower unit again, pulled the thermostat, I now wanted to test for blockages so I ran water up the brass tube and saw it come out the thermostat hole and the pressure relief hole so I know there are no blockages there. I also have ordered an new impeller and a new housing. If this overheats again, I don't know what else to do. How does the head get cooled? Does the water pressure push the spring back and circulate in the head until the thermostat opens? Where does the water go from there??