Newmar generator

I looked at a 2000 Newmar Dutch Star yesterday that was absolutely clean as a whistle, it was owned since new by a seniors couple which I'm not all that far from, anyway they started the diesel generator and I was surprised how loud it was (deal breaker),just terrible. I asked if it was a Onan, they said Kubota, is that so and are they that loud or do they have adjustable rockers? BTW it was a 38' single slide, 2 year old tires and 55k miles for 48K dollars and clean inside and out. They even waxed the tail light lenses