Onboard generator install

[motofan91]

Looking to install an Onan 4k genset.. I do know that the toy hauler has the generator prep package. mostly looking for info on mounting the unit inside the compartment.. Dowe the sheet metal box need to be removed completely or just the floor to access mounting holes, etc?...Any photos or info that you guys can provide will be extremely helpful..
Thanks in advance!

[Kristian]

I talked to the company that installs generator for puma and they said you have to cut out the floor of the box and there is supposed to be mounting holes for onan under it

[BBQGUY]

I installed one in a 2016 359thks last year.
It will help if you post which unit you have.
If you can afford the 5500 Onan it is worth the extra money.
As posted above, you will have to cut out the bottom of the generator box. Under that will be the mounting frame for the generator. Have you looked under the toyhauler to see what is under the generator box? There maybe another sheet of steel that you have to cut.

[motofan91]

I forgot to add.. its a 351THSS..
I will get the floor of the box cutout to start with.. there is a solid sheet of steel underneath so I will have to clearance that for the exhaust as well?
Thanks for the replies.

[BBQGUY]

Remove the bottom of the generator box. Tape all of the cut edges of the box or get a box of Band-Aids. Later you may/will have to cut the lower half of the left side of the generator box to access the fuel and return lines.

From the top drill 4 holes in the lower sheet metal at the corners of the bottom of the generator support. Its about 4" below the top of the generator support frame. A step drill bits works well for this. The holes need to large enough for a sawzall metal blade or what you will be using to cut the metal. Even if you are using a grinder, cut the holes for reference lines so the bottom can be removed up to the edge of the lower generator support frame. If you have access to a plasma cutter you're golden.

Mostlikely your transfer switch is located under the passenger side step to the bed above the pinbox. There will be drywall screws through the carpet on the top step and on the first riser which are screwed into the floor at and angle. A rare earth magnet works well in finding the screws. Now would be a good time to install a Progressive EMS unit. It will fit next to the transfer switch. The EMS goes in the park power line before the transfer switch.

Sometimes there is a junction box near the generator box, if not, you will have to drill a hole near the upper left corner of the generator box to feed the wiring. This will require a sealed electrical conduit connector available at the home improvement store. For many reasons we installed a plug in the power line between the generator and the transfer switch. This came in handy when house power was lost for 2 days after a hurricane last year. Made a breakout box with duplex outlets and used the generator with drops cords to keep the fridge and freezer running.

This is also a good time to consider the location of the remote start switch/hour meter if you will be installing one.

If is very important that you check and seal completely around the generator box where it meets the living quarters to prevent any of the exhaust gasses from entering the RV. Consider installed a second carbon monoxide detector in the living room as a safety precaution.

Make a template of the bottom of the generator and test fit. This step quickly showed us our generator box was not located correctly over the generator support, the box was shifted 4" to the left side. This required us to cut slits at the front and rear corners on the right side of the box so the generator would fit. Even with that, we also had to drill new holes in the generator support frame to match the bottom of the generator and trim the top of wooden frame member located under the lower front of the generator box.

Other things to consider.

Get the 5500 generator; in the future when a second AC is needed you will not have to replace the generator. The 4000 will not run 2 ac's.

Before installing the generator and its easier now, add a divider under the generator support frame to separate the intake air from the hot exhaust. Had a welder friend who cutout the bottom for us, he used this scrap piece to make the divider and welded it in place. This will make a difference in keeping the unit cooler.

We took the RV to a muffler shop which made and hung the exhaust pipe to exit the drivers side. The cost is much less than the pipe from ONAN and is custom fitted.

Another good thing to do is remove the fuel filter and replace it with a 1/4" hose barb to add an inline fuel filter and fuel cut-off. Makes maintenance much easier. WIX Filters - 33001 works well. Change the filter after the first 20 hours of use. There will be stuff in the tank that will clog it. If you add fuel stabilizer in the tank and exercising the generator monthly it will serve you well for years to come.

So how do you get a 250 pound generator in the RV? Place the generator on a piece of plywood on the tailgate of the TV, back up to the trailer, raise/lower the front jacks so the generator is just higher than the opening and push.....
Good luck.
PM me your number if you want to talk.

[motofan91]

Thank you for taking the time to write that detailed procedure. It covers most all of the questions I have and hopefully will help anyone else that would be doing this installation.
As I begin if there are any questions, I will be in contact.
Thanks again!

[Kristian]

Can you post pictures of your progress

[larrytbm]

I have a related question, are the fuel and return lines already hooked to the fuel tank? I am not planning on installing a generator, but would like to use the gas tank for refueling. However I'm not sure I like the idea of having fuel in the lines running the length of the RV if there is no generator.

I'm thinking about removing the metal box entirely, looks like it is just stapled in along the front edge. But the baggage door has to be removed first, then re-installed and recaulked.

[BBQGUY]

The fuel and EVAP lines to the generator are connected to the tank. The lines are capped at the generator end. It's doubtful that fuel will enter the fuel line. It cannot enter the EVAP line. You can crimp the fuel line somewhere near the tank it you like.

To remove the generator box you will have to remove the door and maybe the front diamond plate.