Onan marquis 5500 generator

OP:

You might want to get yourself a Kill-O-Watt meter:

https://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU

You just plug it into any electrical outlet and it will tell you if you what kind of volts and hertz you are getting from your generator into your RV.

2manytoyz wrote:
It should bog a little when a heavy load is first applied, but once the A/C is running, it should stay stable. If it is continuing to bog afterwards, most likely a dirty carburetor. It's starving for fuel under load. You might get lucky, and find that it's just a dirty fuel filter.

While this is a very popular generator, no rebuild kit is available that I could ever find. Ultimately, I replaced the carb on mine. Not overly complicated. Runs perfectly once again.

Believe it or not, we had these exact same symptoms and the Onan tech ended up determining my carb was letting TOO MUCH fuel through. He replaced the carb under warranty and things run beautifully now.

--

Unrelated, you might want to double-check Amazon affiliate rules on putting affiliate links on forums. I do a bunch with it and it seems that you are only supposed to share them on sites under your own control (or for social media, under accounts that you fully control).

My understanding that what you're supposed to do instead is create pages on your own website that then have the affiliate links, like this:
https://learntorv.com/drinking-water-hose/

Note, sharing affiliate links in posts is often also outside of forum guidelines. I have no idea if it is or isn't here on RV.net but I know it's not allowed other places.

Thank you to everyone who replied I have some idea what to do next..appreciate it.

It should bog a little when a heavy load is first applied, but once the A/C is running, it should stay stable. If it is continuing to bog afterwards, most likely a dirty carburetor. It's starving for fuel under load. You might get lucky, and find that it's just a dirty fuel filter.

While this is a very popular generator, no rebuild kit is available that I could ever find. Ultimately, I replaced the carb on mine. Not overly complicated. Runs perfectly once again.

Here's a video of the job: https://youtu.be/DUEthYuKGMk

Source of parts:

Onan carburetor: https://amzn.to/2HgqRFk
Onan air filter: https://amzn.to/2tO8C22
Onan fuel filter: https://amzn.to/2SM1KMK
Onan fuel pump: https://amzn.to/2tNtvKM
Onan oil filter: https://amzn.to/2XI4luC

Deleted - double post

When the A/C's start they draw a LOT of power.. You may need a tune up on the Genny or on the A/C for that matter.

But an A/C that draws say 1600 watts running can easily draw 6000 watts starting. Your genny is 5500 so that's puting it in "Surge rating" range.

If your A/C does not already have it.. Add a Soft Start Kit to it.
That should help Oh. SOme companies call 'em a "hard Start Kit"

Fixes a hard start. makes it a soft start. Yes it's confusing 2 names for same thing.

I had a Kohler 4000 generator that was doing the same thing. After doing all the repairs you mentioned I replaced the voltage regulator and it was fixed. The dealer where I bought the RV did the diagnostics and then I got the part and did the installation.
Good luck with yours.
Bob Cabanas