Converting Onan generator from gas to propane

In answer to the question "CAN it be done," the answer is yes. There are propane conversion kits for gasoline Honda generators. So converting gasoline to propane is possible.

The question "HOW is it done" is beyond my skill set. But, you may want to contact Hutch Mountain, they are one of the larger gasoline to propane conversion companies, and ask if they can help.

There are kits to adapt an Onan to run on propane. Last time I looked they weren't all that expensive even. And didn't look all that difficult to install, but on a motorhome, access could be an issue.

To make it feasible on a class A you'll also need to install a much larger propane tank. Mine is 65 gallons and is expected to provide about 50 hours runtime. I've never tried it that long.

I believe such horror stories involve portable generators and installed generators that rarely run. Proper regular exercise of a generator should prevent carb gumming.

Also getting motorhome non-removeable propane tanks filled can be a major pain..

Do you think the number of “horror stories” significantly out number the instances of people who have had zero issues? Of those with issues, how many have to do with fuel source versus issues due to no or poor maintenance?

It will make you sleep better than swap.

A Gasoline powered Onan is exactly the same as a LP powered. The ONLY difference is fuel to run it Gasoline or LP. You read about problems with Gas powered Gensets because they are probably 95% of all RV Gensets. The ONLY problem with Gasoline Powered Gensets is the USERS fault, not a design problem. Gasoline Gensets need to be run at least 1 hour a month. This keeps the fuel from deteriorating and gumming up the Carb fuel jets. Same is true for Home lawn equipment. Don't properly treat and store your Gas powered Home appliances, you will have a ruined appliance. Having a LP powered Motorhome in a Gasoline and Diesel powered Motorhome LOWERS its resale value. LP powered gensets are limited by the size of the ASME LP tank on the motorhome. Usually the LP tank has no more than 25 to 27 liquid gallon capacity. LP powered Gensets consume 1.1 gallons LP at full load and about .7 gallons at 1/2 load. So this gives you at best 20 to 24 hours before LP tank refill. Even less if you are using onboard LP appliances. Gasoline Powered gives you 80% of the Gasoline tank capacity at .9 gallon 100% load and .6 at 50% load. You could go 3 to 5 days 24 hours a day. AND, LP gensets are also prone to problems from gummed up LP regulators. Especially when it is hot outside. Doug

hedgehopper wrote:
I am considering the purchase of a Class A with a gasoline-fueled Onan generator and have heard a lot of horror stories about problems with such generators.

Here's a funny story to counter your internet wisdom about the horror stories of gas powered Onans.

Camper in sig, bought last year. Orig owner literally used it like once or twice the first year and it sat since 2017/2018 unused.
Had it advertised as a propane generator.

As I really didn't want LP gen and also didn't believe him, I asked multiple times. (Camper is 300 mi away at this point, can't just run over and check it out) Answer was the same. "I've started the generator several times, and have to turn on the LP, light the stove and only then will the generator start!"
(Some of you will be really laughing by now...)
Regardless, I head out to inspect and buy it.
He goes through the whole deal lighting the stove to fire up the genny.
Turns out he had NEVER added gas to the gas tank. There was apparently just enough gas still left to run the generator (from the selling dealer when new??) as it read empty and the fuel station pump only pumped air.

Bottom line, that generator actually fired up and ran somewhat acceptably on what had to be 4 year old gasoline!
Not recommended, but....it runs much better on gasoline purchased in this decade!

FWIW, we had a built-in Onan 5500 in our last toyhauler. We owned the trailer for 10 years, and had about 60 hours on the generator. I ran it rarely, but always drained the carb when I was done with it. It was never run regularly, but also never failed to start when needed. If you don't drain the carb and only run the generator irregularly, you'll very likely have issues. There was never any fuel in my Onan's generator when it was sitting idle. Not a good practice, to not use it regularly, but it worked for me. Maybe just good luck.

The key to any gasoline gen is using non ethanol gas. Or proper fuel stabilizer.

I would love to change my CUMMINS Commercial LP 6500 gen to gas. It’s VERY THIRSTY.

Cummins12V98 wrote:
The key to any gasoline gen is using non ethanol gas. Or proper fuel stabilizer.

Most motorhome generators are plumbed into the chassis fuel tank(s) - which means that you would also have run the motorhome engine on non-ethanol gas. Every time you fueled the motorhome up, you would be paying a lot more.

One of the best strategies for running ethanol gasoline in generators is to shut off the gasoline supply (i.e., install a fuel cutoff valve if none is already present) immediately prior to long-term storage, and then run the engine until it has consumed all the remaining fuel in its carb bowl.

If the generator engine has an electric fuel pump, you can install a "winterize" switch to manually shut it off while the engine is running, thereby accomplishing the same thing as installing a fuel cutoff valve.

Naturally, you don't want any AC electrical loads connected to the generator while doing this, because the engine will stumble and surge as it runs out of fuel.

Some engines have a fuel drain screw on the bottom of their carb bowl. Temporarily opening this screw drains all the gas out of the carb.

Basically, the idea is to avoid storing the generator for long periods with any gasoline still in the carburetor. The ethanol in the gas attracts water (which corrodes delicate parts in the carb), and the more volatile components in the gas gradually evaporate, leaving varnish behind.

hedgehopper wrote:
I am considering the purchase of a Class A with a gasoline-fueled Onan generator and have heard a lot of horror stories about problems with such generators.

A good friend who travels with me quite often has a DP with a propane genset.

The heartaches of trying to find LPG, constantly, is a BIG issue. In cold weather he’s burning propane for heat AND the electricity to keep the heat running.

I don’t know how big his tank is, but in ‘heating season’ he’s refilling his LPG every other day.