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Onan MDKD 7.5


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  #1  
Old 03-16-2017, 01:54:07 AM
TLB01 TLB01 is offline
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Default Onan MDKD 7.5

My MDJC is overkill...Thus enter the Kubota dragon. 2 may enter. One will leave (sold). It has the usual Marine surface rust, but it makes power without a flinch. Just need to get a Donaldson on it and a different exhaust solution. I would like to say that I can't believe these came with a cheap plastic intake resonator on them...but they did.

Anyway. No pics. Not unloaded.
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Old 03-16-2017, 11:17:06 AM
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Default Re: Onan MDKD 7.5

Resonator maybe because it is a marine unit?
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Old 03-16-2017, 01:06:36 PM
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Default Re: Onan MDKD 7.5

Yup. Its a marine unit. Its (the resonator) just what can only be best called a place holder really, as its not really sealed or secured. Its just sort of there, being cheap and plastic that is cracked. Are boat bilges really considered dust free? The only other machines that eliminate air filters completely by design are snowblowers and I get that.

There are plenty of Kubota parts out there so other than the obvious addition of a radiator, I need to make this guy not ingest dust etc. Does anyone know what model Kubota 3 cylinder these were built with? Just in general? All I have is an educated guess.

---------- Post added at 10:06:36 AM ---------- Previous post was at 09:57:11 AM ----------

Looks like it might be a D950B.

As stated before, its not unloaded yet so I can't see the plate. I did order a parts manual for a 950 engine. Hopefully there is a side exhaust manifold and top inlet intake so I can put the air cleaner can and muffler outside of the sound enclosure.
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Old 03-16-2017, 01:15:08 PM
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Default Re: Onan MDKD 7.5

I believe it's a D950 also

Manual:

http://www.twinslan.net/~n0nas/manua...0(06-1995).pdf
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Old 03-16-2017, 02:10:45 PM
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Default Re: Onan MDKD 7.5

Or I could be totally wrong. Since I am wrong more often than not.

4.0MDKC-3CR/1A
Serial J850782377

It can be made to do 120/240 according to the lid diagram and its the transformer regulator. Tested it with some power tools.

4KW is not much power. Almost seems like this MDKC should go back in a boat after a good clean up. Someone else's boat.

15KW is more power than I need and 4KW is not enough. Fantastic....

Advice? Cut my losses (or maybe bait would be a more appropriate term) and just sell it as is for whatever I can get? It has 286 hours on it but has some rust because its a Marine gen thats from the 80's. Seems like selling BOTH is probably a good idea.
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Old 03-16-2017, 02:25:46 PM
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Default Re: Onan MDKD 7.5

The title in this thread is a 7.5 MDKD so I thought you were asking about that. Where did the 4.0MDKC come into play???

3CR is a 120/240 voltage code reconnectable to 120 only
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Old 03-16-2017, 02:33:29 PM
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Default Re: Onan MDKD 7.5

It came into play because I am an idiot? Thought I had 1 thing. Turns out it is another. Very frustrating and now very public blunder. Makes me wonder if I should just stick to Hondas like a good suburbanite and leave these Onans alone.
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Old 03-16-2017, 02:39:49 PM
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Default Re: Onan MDKD 7.5

Way too many in my collection to forget about!

So re ask your question again, what are you trying to find out????
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Old 03-16-2017, 02:47:43 PM
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Default Re: Onan MDKD 7.5

Well, it this point I have to find out what this mdkC engine is. It only has 675 CC cast on the block. So its NOT a D950. Its something else.

That is if I still want to consider converting this for land use. Its not like I don't enjoy working on this sort of thing. Its just a manner of what state it needs to be in if I am just going to re-sell it while I finally arrive on what configuration of Gen works best.

I don't need 240 volt supply for the house as even now my current set up is 240 30 amp twist lock split on two hot legs to a transfer switch that is only set up for 120v distribution anyway. Still if this only can output 120 to one leg, than its not going to work well with the transfer switch.
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Old 03-16-2017, 03:20:04 PM
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Default Re: Onan MDKD 7.5

The 3cr should be able to configure all the output to 120v or 240v by switching a couple of wires in the control box. I actually found I could run my place on 3Kw but I have an all gas house and no well pump or sewage pump. Bummer about it being a DKC instead of DKD but they do get excellent fuel economy. I have only had one of the smaller units & they do look identical to the 7.5s . That said I had no trouble selling it to an off grid guy, they want the smallest diesel gen possible to keep fuel costs down, usually a backup to solar and almost no one has 4K of solar. I tried advertising in the interior areas of the province and sold several small units there. Cheers Dan
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Old 03-16-2017, 03:34:24 PM
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Default Re: Onan MDKD 7.5

Looks like it might be powered by a Kubota D650 engine.

---------- Post added at 12:34:24 PM ---------- Previous post was at 12:26:55 PM ----------

Yah from what I have read so far it uses .25 gph of fuel at half load! That's amazing!

My whole pad can run fine off 2-3KW with reasonable load management. So that MDKC definitely has some major pluses, such as its really small, really quiet, really thrifty and really bomb proof. Its got the transformer regulator so no control board either so its really simple. There is the matter of the intake and exhaust manifolds really need to be changed for land use however. I don't think I want to keep the complex plumbing for raw water and captive water. Too many failure points with that IE: leaks.
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Old 03-16-2017, 04:00:22 PM
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Default Re: Onan MDKD 7.5

You can disconnect the raw water cooling from the exhaust and either leave the jacket cooling on the exhaust or disconnect it too. Just run a regular muffler attached to the exhaust piping and punch a hole in the soundshield to bring the pipe out. . The marine manifold will work fine and be a little quieter than the non jacketed manifold. I usually remove the raw water pump from the back of the injection pump drive and use a block off plate. The standard Kubota water pump will work fine to pump through one of those aluminum Honda rads and the little 12V alternator has plenty of jam to run the fan and leave some leftover for battery charging. You can mount the rad to the front of the soundshield or on a L bracket attached to the base. You can put wheels attached to the base to roll it around. If you have the soundshield it will be as almost as quiet as an inverter gen without the complexity. Cheers Dan
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Old 03-16-2017, 05:48:23 PM
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Default Re: Onan MDKD 7.5

Think this might count as a good mistake. There is no well pump or sewage injector to worry about. Just a fish tank, some lights, the TV, modem/router, a fridge and the pellet stove. Pellet stove is the most important and it can run off a Honda EX350 2 stroke inverter if need be since it draws so little power. 4K will be plenty and the fuel/space savings will be monumental.
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