if thermostats looks like that the poppit valve is bad too. Youtube it and it is easy to do. If it is stuck open it will not let it the water flow through the engine at full pressure. Like I said before had to pull my power head off and that is where the problem was. If exhaust gasket is blown it will let exhaust pressure push back into the water jacket and at high rpm that pressure is more than water pressure. But that is very rare for that to happen only seen it twice

Have not tried yet. Anytime im not working I want to be fishing. On days now for awhile so gonna try fixing in evenings before I get my one day off and then start night so I can fish again.