I have experienced this twice. First time with my 28 foot Weekend Warrior. Same generator as yours. When it got hot out that thing would just over heat just like yours is. I just sat a small small fan under it blowing up and never had another problem. Ran hundreds of hours like that in 90+ heat. On my 36V Jayco Recon it was fuel pumps. The Onan pump would overheat and die. After the second one I went to Auto Zone and bought a $30.00 electric pump and placed it back at the fuel tank where it should be. Electric pumps push fuel great, but really cant pull fuel and over heat. I used a 3 to 4 PSI pump. If you do this just check and see what psi the pump in your genny runs at. Some Onans are 2, some are 4. Mine has been running hundreds of trouble free hours like this.