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Old 07-26-2020, 12:18 AM   #1
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Upgrading Onan 4000

Hello, we recently purchased our first Class C and are looking at making some improvements. It's a 2018 Thor Four Winds 28Z that we bought from a company that used it as a rental. The current Onan 4000 is at 577 hours, and takes a few seconds to start. It clanks, chug, clank, start. When turning it off, it shakes the whole coach and makes some interesting sounds. My previous travel trailer had an external Honda generator that was excellent and was quiet, started easily, turned off easily. The company mentioned they maintenanced the generator earlier. I suspect (with no real facts) that the generator might need to be replaced soon. Rather than replacing it with another 4000, I am curious if we could upgrade it to a 5000 without much of an issue. Am I way off base with thinking about replacing it?

Additionally, I read some folks recommending to change a 30amp coach to 50amp. What are the benefits of doing so?

Thanks!
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Old 07-26-2020, 12:36 AM   #2
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577 hours is nothing on a generator.
Are you priming the generator before you start it?
Have you checked the mounting points on the generator?
You would need to do some major modifications to fit a 5500 generator in a 4000 slot.
A 30 amp RV can handle 3600 watts
A 50 amp RV can handle 12000 watts
Going from 30 amp to 50 amp requires major electrical modifications.

If you want an RV with 50 Amp service and a 5500 generator you should trade your current RV in on the purchase of what you want. After spending the effort and money on converting your used rental you would have an RV that is now worth less than you originally paid for it due to the modifications.
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Old 07-26-2020, 12:57 AM   #3
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Quote:
Originally Posted by 16ACE27 View Post
577 hours is nothing on a generator.
Are you priming the generator before you start it?
Have you checked the mounting points on the generator?
You would need to do some major modifications to fit a 5500 generator in a 4000 slot.
A 30 amp RV can handle 3600 watts
A 50 amp RV can handle 12000 watts
Going from 30 amp to 50 amp requires major electrical modifications.

If you want an RV with 50 Amp service and a 5500 generator you should trade your current RV in on the purchase of what you want. After spending the effort and money on converting your used rental you would have an RV that is now worth less than you originally paid for it due to the modifications.
Ted/Melinda, thank you! You have some great points, and exactly my worries with both aspects. I totally forgot about the priming of the generator. I'll try that next time I go to turn it on! As for the mounts, I'll check those as well and being 577 hours, I saw on the manual at 450 hours to replace the spark plug, so I plan on at least pulling it out and looking at the condition of the spark plug. I guess maintenance on the RV can be my quarantine project!
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Old 07-26-2020, 11:31 AM   #4
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One more thing: Welcome to the forum!
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Old 07-26-2020, 12:40 PM   #5
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I agree with 16ACE27.

Do a mini tuneup (plug, air filter, oil change, fuel filter). I did one for mine just because I like to be on top of thing. Not very hard. I only have like 175 hours on mine. I always have fuel stabile in my tanks when in storage.

I prime mine for 30 / 45 seconds, then I wait about one minute or two (by doing something else like closing the storage building door, doing a walk around outside etc) and it will fire up usually on the 1st or 2nd attempt.

I cant tell any difference with my mini tuneup (it ran fine before) but i noticed the spark plug gap was about 2x that of what the book calls for.... so that might be a problem for you with all of the hours you have?

I also adjusted the carb for my elevation. So that might help you as well.

It does shake some when shutting down but the Genny is absorbing most of it. You can shake it (while off so its not hot) and they move quiet a bit.... thats how its designed.
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Old 07-26-2020, 07:40 PM   #6
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So I checked out the bottom of the generator and tightening all of the screws to help with the vibrating of the coach when the Genny turns off. This star-bit bolt has a large rubber grommet with a washer. Looks to be used to absorb some of the vibration given the grommet. There are two of these bolts, and they're screwed all of the way in. But the grommet isn't even absorbing anything and isn't touching anything. It just spins. What part is this? I looked through the underfloor kit parts, I looked through the generator parts manual, but I can't find it. I worry the folks I purchased the RV from put this part in here and it doesn't belong.


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Old 07-26-2020, 09:20 PM   #7
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Quote:
Originally Posted by 16ACE27 View Post
577 hours is nothing on a generator.
Are you priming the generator before you start it?
Have you checked the mounting points on the generator?
You would need to do some major modifications to fit a 5500 generator in a 4000 slot.
A 30 amp RV can handle 3600 watts
A 50 amp RV can handle 12000 watts
Going from 30 amp to 50 amp requires major electrical modifications.

If you want an RV with 50 Amp service and a 5500 generator you should trade your current RV in on the purchase of what you want. After spending the effort and money on converting your used rental you would have an RV that is now worth less than you originally paid for it due to the modifications.
This got my attention. I have a 30A coach. There have been times when I've plugged up to 50A in situations where 30A wasn't available and open sites had 50.

Are you saying you shouldn't do this? I was plugged up to the 50A pedestal all winter in Tucson and nothing happened. Was it shear dumb luck?

Please elaborate.
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Old 07-26-2020, 09:25 PM   #8
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Originally Posted by The_Breeze View Post
This got my attention. I have a 30A coach. There have been times when I've plugged up to 50A in situations where 30A wasn't available and open sites had 50.

Are you saying you shouldn't do this? I was plugged up to the 50A pedestal all winter in Tucson and nothing happened. Was it shear dumb luck?

Please elaborate.
I think what they mean is that converting the whole RV to a 50amp from 30amp shouldn't be done. Not that plugging into a 50amp from a 30amp coach is a bad thing.
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Old 07-26-2020, 09:46 PM   #9
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Originally Posted by eccentricson View Post
I think what they mean is that converting the whole RV to a 50amp from 30amp shouldn't be done. Not that plugging into a 50amp from a 30amp coach is a bad thing.
Got it. Thanks.

But then you wouldn't have to do that unless you planned on installing a second A/C and run them both at the same time?

Everything else should remain copasetic.

I still think Ace might be right about trying to shoehorn a 5500 into a 4000 cavity, but then we used to run 283's and 327's in Vegas back in the day. And I personally saw a 283 in a Healey Sprite once. Engine stuck out of the hood but that was cool back then.
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Old 07-26-2020, 10:15 PM   #10
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Originally Posted by The_Breeze View Post
Got it. Thanks.

But then you wouldn't have to do that unless you planned on installing a second A/C and run them both at the same time?

Everything else should remain copasetic.

I still think Ace might be right about trying to shoehorn a 5500 into a 4000 cavity, but then we used to run 283's and 327's in Vegas back in the day. And I personally saw a 283 in a Healey Sprite once. Engine stuck out of the hood but that was cool back then.
Oh, I'm sure in can be done, just like putting those small blocks in the Vega; but it does require some "modification". Somehow the engine mounts just won't line up.
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Old 07-26-2020, 10:20 PM   #11
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Oh, I'm sure in can be done, just like putting those small blocks in the Vega; but it does require some "modification". Somehow the engine mounts just won't line up.
Probably right and not worth the effort. If the 4000 goes, replace it with a 4000. The only way 577 would ruin a gen is if it wasn't properly maintained.

The small blocks in those Vegas? Snap your neck in two and a $100 bill on the dash when the driver said go usually left you empty handed.
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Old 07-26-2020, 10:21 PM   #12
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It's funny that you mention the V-8 Vega combinations.
I knew a guy who force-fit a really built 427 into one of those little card.
The very first time he fired it up: he revved it a bit...
The hood, tailgate, and both doors popped open!
He also had the windshield pop out also!
He twisted that poor little thing like a pretzel!
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Old 07-26-2020, 10:23 PM   #13
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Originally Posted by Bob Denman View Post
It's funny that you mention the V-8 Vega combinations.
I knew a guy who force-fit a really built 427 into one of those little card.
The very first time he fired it up: he revved it a bit...
The hood, tailgate, and both doors popped open!
He also had the windshield pop out also!
He twisted that poor little thing like a pretzel!
I'm sorry...LMAO

Remember Brutus? The 426 Hemi Opel GT?

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Old 07-26-2020, 10:29 PM   #14
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He spent a ton and a-half's worth of large bills to get to that point.
The firewall was moved back, the passenger compartment was shortened to the point that the back seat was now the front seat, the track was widened, the headers came out through the front fenders, and the battery and radiator(s) were moved to the trunk.
I don't have any idea what he used for a front suspension: but that was the biggest challenge!
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Old 07-26-2020, 10:35 PM   #15
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He spent a ton and a-half's worth of large bills to get to that point.
The firewall was moved back, the passenger compartment was shortened to the point that the back seat was now the front seat, the track was widened, the headers came out through the front fenders, and the battery and radiator(s) were moved to the trunk.
I don't have any idea what he used for a front suspension: but that was the biggest challenge!
He probably welded or built a new subframe. Back then, you went to a junkyard and scavenged parts. A big block subframe would have widened the track. The twisting tells me he didn't install subframe connectors or the torque was simply too much for the construction. He probably should have sat the body on a tube frame, used a four link out back and rack and pinion out front with matching springs, shocks, etc. Ladder bars would have worked out too.

There used to be a guy out here - GMTech something - that stuffed a FI 5L in a Saturn. He stopped coming here but that was one hell of a car.
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Old 07-26-2020, 11:25 PM   #16
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Those were the good ole days. With a "hot wrench", and a hacksaw: the sky was the limit!
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Old 07-27-2020, 04:52 AM   #17
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I neglected to say thank for your offer. I laid subtleties aside for a minute to get the rest out and forgot to put them back.

It would be nice if we cross paths some day.
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Old 07-27-2020, 12:51 PM   #18
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I helped a friend mount a 350 inside a vega station wagon. He kept blowing rear ends so I told him to get a junk yard monza rear end since the monza had a v8 and it would fit in place of the little vega rear end. Solved that issue. Then he had a problem burning out tires so he finally sold it. It was just too light to handle. It was a fun project.

Paul
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Old 07-27-2020, 01:38 PM   #19
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I'm going to repost this, the thread got a tad off topic and I'm still lost on where to going these two bolts.

Quote:
Originally Posted by eccentricson View Post
So I checked out the bottom of the generator and tightening all of the screws to help with the vibrating of the coach when the Genny turns off. This star-bit bolt has a large rubber grommet with a washer. Looks to be used to absorb some of the vibration given the grommet. There are two of these bolts, and they're screwed all of the way in. But the grommet isn't even absorbing anything and isn't touching anything. It just spins. What part is this? I looked through the underfloor kit parts, I looked through the generator parts manual, but I can't find it. I worry the folks I purchased the RV from put this part in here and it doesn't belong.


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Old 07-27-2020, 03:24 PM   #20
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Those could be the spark arrestor clean out plugs as per the diagram from the onan manual.

Paul
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