I recently purchased a 2010 38ft Zinger Destination model. 2nd time out my wifey noticed that the hot water was not as hot as she'd like, and it was taking about 2-3 hours to warm up from and empty tank. We had it on electric, I switched the tank to propane. It roared continuously for at least 30 mins. When I went out to check on the heater, water was being forced out of the releif valve? Do I have a problem with the thermostat? I have contacted my dealer, but as of today have not heard back. Any ideas?