Question

I have a 24 ft glastron boat that only had 5 hrs on it when I bought the boat it ran fine but started to over heat after I did a fresh water flush . I emailed the company and they told me that the impeller must be bad so I did change it and also changed the themastat. The boat is a 2003 the motor is a v8 volvo io and they said that from sitting the impeller must have gone bad. The boat ran fine after i changed the parts my son does not flush the motor so about two weeks ago i used the boat the last time the boat was used I did a fresh water flush and now it over heated. There is a hook up for the fresh water on the motor I thought that the intake waterports may be blocked but they were clean . I do not know were to go from here the tech at the company has no idear could you help.