Replacing Onan Generator

It all depends on the size of the opening, the size of the generators, the location of the mounting points, etc. Someone will have to evaluate the MH and generator to determine that.

If you have the Honda manual, see what it says about clearances when mounting the generator in an enclosure. It might fit just fine but if you do not have the proper spacing for sufficient cooling air flow, it won't last long.
You also will probably have to modify the exhaust so that you have a bottom exhaust and then see what you have to do to make the inside dash starting switch operational.
Naturally you will want to insure that once it is mounted, you can easily remove the covers to do routine maintenance.

If the Honda will fit the hole, then all you need is the capacity to cut and weld, do the necessary wiring and run a fuel line. It's usually much easier to repair the in place item then replace it with something of different design.

Richard

I have build-in Generac, yet I carry quiet Honda 3000EI in my bays to use it instead.
Generac is very loud and takes 1 gallon of gasoline per hr.
Honda is hard to hear and 2.4 gallon tank will run it for 12+hr.
Replacing build-in would make me doing lot of homework.
Is the Honda you are considering an inverter, quiet generator?

Lots of good points. I hadn't considered the maintenance aspect, but that would be a consideration. I have welding skills, so that is doable. The main thing I'm looking to do is reduce the noise and get a lower-hour generator into the space. I'll have to continue to evaluate. Thanks for the input thus far.

Tom

I think you will find it would be easier to fix the Onan. Nothing about Honda is compatible with on board generating, such as exhaust, cooling, etc.