I have one that I use on our Bertram. It powers the refrigerator, battery charger, and the water heater when we're out on the hook. The water heater is only a 750 watt unit but gets the job done just fine. I put it up on the forward deck and run the cord back to the power inlet in the cockpit. No fumes. You can't hear it running most of the time. Very simple. Best part is that I use it at home when the power goes out.
I have one also. Noise isn't an issue the big concern is CO. If you run the genny up on the foredeck make sure you keep your hatch and windows closed. I'd also put a CO detector down below in the cabin.