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15KW marine onan diesel good for backup at home?


I am looking at a 15Kw onan (15.0 MDJF 3CR/2268AA) as a potential backup unit for my suburban home....

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Old 01-12-2007, 02:12 AM
bigblockchev bigblockchev is offline
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Default 15KW marine onan diesel good for backup at home?

I am looking at a 15Kw onan (15.0 MDJF 3CR/2268AA) as a potential backup unit for my suburban home. The unit has 3900 Hrs on it has manuals and extra filters with it. I believe it to be a 120/240 single phase unit ( has 2 legs and a grouded neutral in the power connection box) It was installed in a Hatteras long range cruiser 1976 vintage. It was replaced last summer by a 13Kw machine. This was due to a decision by the owner to upgrade, they run a wilderness charter buisness. They had an appraisal done , did some work on the engine, new heat exchanger repaired a leak on the raw water pump and then did a load test on it. It was found that there was a coolant leak in the head gasket region when full load was placed on the unit. At half load there was no leaking. Rather than repair this they decided to replace it. They have a good current oil test report from CAT. The comment was made that the unit smokes for the first 30 secs then cleans right up. The machine itself is fairly tidy. I am hoping to see it run in the next few days. I would solicit comments from the members on this setup, anything to watch out for? known problems with this model. I intend to get a decent size rad for it and put some sort of 4cyl car muffler to quiet it down and run it on homebrew B100 like all my cars. Anyone have any advice for making a sound absorbing enclosure, materials design, other considerations. I throw this out for comments feel free to elaborate and thanks
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Old 01-12-2007, 02:49 AM
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Default Re: 15KW marine onan diesel good for backup at home?

3CR would be the reconnectable 4-wire output, 120 2-wire or 240 2-wire or 120/240 3-wire, quite a useful configuration.

The smoke on start-up probably means it has some ring/bore wear, but it also might need a decent run at full load to get the rings bedded down after a lot of low-load running.

I'll be getting the MJDA/B/C schematics up on the Onan section soon, there is one for the 3CR configuration in there.

Rockwool is a good sound absorbing material, we used it behind perforated ali sheet with polythene between to keep oil out.

Peter
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Old 01-12-2007, 07:13 AM
Jim Rankin Jim Rankin is offline
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Default Re: 15KW marine onan diesel good for backup at home?

It might be worth a try to retorque the head bolts, CAREFULLY, and try a block sealer. If that doesn't stop it, you could probably fix it for the cost of a head gasket set and have the head checked/valves ground while you have it off.

If you have a wet exhaust, that will add a lot of heat that your radiator has to handle, so get plenty of capacity there. A electric fan can be the easy way to get a fan on an engine that never had one. this could be a DC or and AC motor. I would tend to go with AC because most of the DC fans are made for intermittent use on the front of a vehicle.
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Old 01-13-2007, 01:17 PM
bigblockchev bigblockchev is offline
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Default Re: 15KW marine onan diesel good for backup at home?

Jim I'm not sure exactly what is referred to as a wet exhaust. There is a cast iron elbow which the exhaust feeds into as well as the discharge from the seawater cooling. Both are fed into some kind of a fiberglass tank filled with water which then discharges through the hull. I had intended to direct the exhaust into some kind of 4cyl car muffler and use a VW diesel rad with some kind of fan to replace the heat exchanger part of the cooling system. Will have to figure out if it needs something different for a water pump or will the existing one be sufficient.

Peter I forgot to ask the fellow if the smoke was black or blue. so excess fuel or oil?

Cheers Dan
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Old 01-13-2007, 03:20 PM
Jim Rankin Jim Rankin is offline
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Default Re: 15KW marine onan diesel good for backup at home?

I should have been more specific about the "wet" exhaust.. What I meant was that some have the exhaust manifold water jacketed to reduce heat radiated into the engine room. this adds a lot of heat to a radiator cooled system that an engine without that water jacket doesn't have to remove. Great for a heat recovery system to heat your house etc. and/or keeping the generator room cool, but not so good with a small radiator.

the coolant circuit through the seawater heat exchanger would be about like a radiator circuit, so that pump should be fine.
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Old 01-18-2007, 12:53 AM
bigblockchev bigblockchev is offline
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Default Re: 15KW marine onan diesel good for backup at home?

Does anyone have an idea what a starter would be worth for this machine. the fellow has offered to throw in a new one with the Generator for another couple hundred , can't find anything similar on the net so I don;t know if this is a good deal or not. Thanks again
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Old 01-18-2007, 11:48 AM
KidDynamo KidDynamo is offline
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Default Re: 15KW marine onan diesel good for backup at home?

Your first post has conflicting information. It was stated that the owner decided not to fix it. It was also said that a new heat exchanger was installed and the pump was worked on.

From a distance, it sounds like a genset that somebody actually tried to fix, was unsuccessful, and now is trying to unload it. New heat exchanger ? Worked on pump? Sounds like somebody tried pretty hard to fix something. It didn't work for them and now you come along.

If it is so easy to fix, have them fix it, absolutely, and then look at it again, without obligation to buy. Will they guarantee it can be fixed with just a head gasket?

Two hundred buck for a starter motor for an older generator that hasn't been fixed? Doesn't sound like any deal to me, either, but then I'm not really familiar with the unit in question.

There are quite a few generators selling every day of the year. I'd try to get one that doesn't need work. If it is old too, the price should be low.

If I buy a fixer-upper, I want to get it cheap, cheap, cheap. That is what they are worth to me. If it was such a hot deal, it would be gone by now.

Just how it strikes me after reading this thread several times.
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Old 01-18-2007, 07:55 PM
dsgsr dsgsr is offline
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Default Re: 15KW marine onan diesel good for backup at home?

ListerDiesel, Ref. the 3CR configuration , Where might I find that. I have a CCKB genset and need the schematic.

Thank you,
David
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Old 01-18-2007, 09:00 PM
Jim Rankin Jim Rankin is offline
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Default Re: 15KW marine onan diesel good for backup at home?

http://www.smokstak.com/forum/showthread.php?t=34814
discusses the reconnection scheme and other issues of loading the generator.
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Old 03-15-2011, 11:51 AM
joethemechanic joethemechanic is offline
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Default Re: 15KW marine onan diesel good for backup at home?

You probably don't want to pay more than scrap money for this unit. The starter is worth maybe 50 or 75 bucks if you need it.

The unit is probably worth $250 in scrap value right now
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Old 03-15-2011, 12:28 PM
markviiisvt4 markviiisvt4 is offline
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Default Re: 15KW marine onan diesel good for backup at home?

Also take not that this is one of those onans that's extra hard to find parts for.
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Old 03-15-2011, 12:41 PM
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Talking Re: 15KW marine onan diesel good for backup at home?

I beg to differ with the previous two posters. MDJx Gensets are GREAT units to build a home Backup Genset out of, IF you are just a little bit of a wrench. They are really easy to setup in a Co-Generation configuration, so as to be able to use much more of the fuel BTUs, than just what is coming out the Copper. Onan built literally hundreds of thousands of these, and most of the basic parts are interchangeable, thru out the DJ Engine Series. Plenty of parts out there, however you do actually have to look around for them. A running MDJF with a YD Genend fitted, is easily worth $1KUS, and they are relatively easy to wrench on. Heck you could get more than that parting the unit out. We have many threads here in the Onan forum of Users who have done exactly this starting with a MDJx Genset, with very good success. Replacing a Head Gasket on the OPs unit is a 3 or 4 hour procedure, for any fair mechanic. YMMV
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Old 03-15-2011, 01:35 PM
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Default Re: 15KW marine onan diesel good for backup at home?

That is a great unit to have. 3900 hours is low hours on MDJF. I have seen some with over 15000 hours on them still running good. Even if you scrapped it out for parts,you could do well. Thousands of them were built,parts are easy to find. You just have to look.
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Old 03-15-2011, 01:43 PM
markviiisvt4 markviiisvt4 is offline
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Default Re: 15KW marine onan diesel good for backup at home?

I have one with a broken governor shaft and housing and haven't been able to find one with out buying a whole unit. Although not to many larger pleasure boats up my way I guess.

Last edited by BTPost; 03-15-2011 at 03:35 PM. Reason: Did you ask here, on the Onan forum?
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Old 03-15-2011, 03:35 PM
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Default Re: 15KW marine onan diesel good for backup at home?

I will contact some folks I know.
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Old 03-15-2011, 08:26 PM
joethemechanic joethemechanic is offline
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Default Re: 15KW marine onan diesel good for backup at home?

Quote:
Originally Posted by BTPost View Post
I beg to differ with the previous two posters. MDJx Gensets are GREAT units to build a home Backup Genset out of, IF you are just a little bit of a wrench. They are really easy to setup in a Co-Generation configuration, so as to be able to use much more of the fuel BTUs, than just what is coming out the Copper. Onan built literally hundreds of thousands of these, and most of the basic parts are interchangeable, thru out the DJ Engine Series. Plenty of parts out there, however you do actually have to look around for them. A running MDJF with a YD Genend fitted, is easily worth $1KUS, and they are relatively easy to wrench on. Heck you could get more than that parting the unit out. We have many threads here in the Onan forum of Users who have done exactly this starting with a MDJx Genset, with very good success. Replacing a Head Gasket on the OPs unit is a 3 or 4 hour procedure, for any fair mechanic. YMMV
Yeah but how does he know it's a head gasket until he tears it down? and 3 or 4 hours labor is worth 300 or 400 bucks around here. Add to that the price of a head gasket (if in fact it is a head gasket) shop supplies, gas to run and pick up parts,,,,,,,,

250 scrap value, plus the value of the repair and he is probably at $750 or so.

Plus he is taking a chance that it needs more serious repairs. I never pay more than iron money for anything I'm taking a chance on.
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Old 03-15-2011, 08:49 PM
Douglas123 Douglas123 is offline
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Default Re: 15KW marine onan diesel good for backup at home?

I agree with BTPost, If you get it. play with it a while,but don't throw anything away. Starter motors for the older units are like gold to me in the memphis area. Have been selling remans for $400.00 But I must have the old starter motor before they get their replacement. Sounds kind of a tough way to do business. I can still get parts to repair them but no source for any new still in the box. Several engines have aftermarket starters with adapter kits. Personally I like to keep them as original as possible
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Old 03-15-2011, 09:12 PM
Wayne 440 Wayne 440 is offline
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Default Re: 15KW marine onan diesel good for backup at home?

Since the original post was in 2007, I expect the set is either fixed or scrapped by now. BUT, as far as I'm concerned any of the J series sets will serve as good or better for small home standby use than anything you can buy today. The trouble is, Cummins is trying to kill the series, both by making parts impossible to get and by using every opportunity to make repairs so expensive that they go to scrap, replaced with a new one.

I have owned several and they have all been good sets. Someday I will try a 30DDA, but it will have to be a good one to displace the DJx in my book.
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Old 03-15-2011, 11:51 PM
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Default Re: 15KW marine onan diesel good for backup at home?

Wayne I agree the 30DDA is a nice unit for a large home backup, etc, at least if you can find one with a single phase generator end. The DDA was on the short list when I was shopping for a generator to put at my elderly mother's house a couple of years ago, ended up finding a deal on a Kohler 30ROZJ which is powered by a similar size, but slightly newer John Deere 4239D vs the 4219D in the DDA.

Ike
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Old 11-16-2011, 09:04 PM
bigblockchev bigblockchev is offline
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Default Re: 15KW marine onan diesel MDJF good for backup at home?

Hi folks it has been a good unit to me. Now it is suffering from the effects of salt water corrosion. The exicter stator failed again , this time it was much more difficult to find the breaks in the windings. I did just barely but it is an iffy repair, In the course of troubleshooting the rotating diode blocks gave up the ghost when I tried to disconnect the nuts to test the diodes individually as per the troubleshooting flowchart. I am wondering if someone has these parts from a failed unit that I could buy. I have a feeling these parts are common to the series. The engine on mine still runs like a champ, I inserted a VW diesel dual fan rad into the cooling circuit so it can be used at home it still has the heat exchanger so can be used to recover heat from as well. Alternativley is there a way to fit something like a "St" generator head to the engine. Cheers Dan
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