My first thought was changing out the fuel filter but I couldn't get the old one out. I have a diesel mechanic friend who is going to take a look at it when the weather dries out some. When I had the spring PM done, they couldn't get the old filter off either and said the fuel line connection was badly stripped and the line should probably be replaced - which requires dropping the generator (the line comes in from the top).
The overspeed problem is a known issue with this generator. If I recall correctly, the generator specialist said it might be a $1000 fix or it could be $4000 - depends. I was hoping a smack with a hammer would solve it.
I checked the specs on some of these industrial/construction generators and they are louder than the Onan. Federal parks have a limit of 60dBs @ 50' and the construction ones were computing out to about 70db but I figured some extra sound insulation would fix that. I just wasn't sure if there was some other reason to not put one in a RV.
Can you even sell a used RV (not that we're selling any time soon) without a working generator? Probably my only use would be to run the house A/C when driving down the road - although the campground we were in last summer lost power during a storm for a couple of hours which is where we discovered the problem.