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Onan 15Kw MDJF vs MDL3

Discussion in 'Generators' started by CaptOz, Feb 2, 2013.

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  1. CaptOz

    CaptOz Member

    Joined:
    Apr 13, 2009
    Messages:
    100
    Location:
    Miami, Fl
    Hi,

    I have a 1986 MDJF 15kw Onan in my boat with a bad electrical end. It has 6000 hrs but engine is fine. I recently did a head and valve job. The eletrical end is a ball of rust but was working until it broke. I have done most of the flowchart trouble shooting so far and all roads point to issue with windings or Diodes.

    Anyhow, I am looking at an MDL3 replacement that is in good shape and I wanted to ask everyone what they thought about the MDL3. This paricular one is set up for 120v but wiring diagram shows how to set up for 240v.

    I spoke with Onan and they told me that because this Generator has a Cummins Engine, parts are obsolete. Not sure if that was just a sales pitch so I buy a new genny. My older Genny parts are also hard to get, but are available for a premium.

    So basically just wanted to get feed back on the MDL3 and its reliability. The MDJF we all know runs forever.

    Thanks,
    CaptOz
  2. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,649
    Location:
    Satsuma, FL
    Diodes are around $45 each pack. Two required (+ & -). If you have the room to pull the end frame off, you can test and maybe fix yourself quickly. If it's the old soldered in Diodes, $.75 (75 cents each) at Radio Shack.
    Either way, You have to get the end frame off for further testing.
    A few hours, 6 pack. volt/ohm meter and you may learn something.

    Then, save up for a new set.

    Amazing, that Cummings owns Onan. Never had a problem getting any OLD Cummings part.

    After trying to fix up old generators for a while now. I have learned they (with room to work) can be fun to work on.
  3. CaptOz

    CaptOz Member

    Joined:
    Apr 13, 2009
    Messages:
    100
    Location:
    Miami, Fl
    Thanks for the input..

    THe Electrical end is a ball of rust. Bad Design on Bertram end.

    Even if Diode are bad. Electrical end wont last.

    Any Comments about the Onan MDL3?
  4. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,649
    Location:
    Satsuma, FL
    http://www.cumminsonan.com/www/pdf/manuals/934-0124.pdf

    At a co$t, Parts should still be available. But where is the smart money going?

    You asking about a 20 year + old set. If it's free and works, Yea, go for it.
    Do you want to go thru an other generators past history (20+ years), fix what you have (do-able), or sleep easy and get a new (or newer) system.

    I'm assuming your thinking like I have to do allot; Boating on a rednecks budget. Been there / done that / lost bux trying to make it work. You need to put a value on your generator needs. The best , smartest, safest, sleep good at night thing I ever did was putting in a new gen-set. 3000+ hours later, two raw water pumps and normal maintance, I sleep sound at night with it running.

    I don't want to sound too negative here, we all do what we can with what we have or can spend, but properly cleaned; you have two artificial reef candidates there.
  5. CaptOz

    CaptOz Member

    Joined:
    Apr 13, 2009
    Messages:
    100
    Location:
    Miami, Fl
    I agree with you. Im not going to take out the pig to put another pig in.

    The MDL3 I have access to is a special unit. It was never put into service and has very little hours. Still havbe original factory oil filter. Sure there is risk with a diesel engine that has not been used in so many years, but it seems to be a pretty good shape. Price is right.

    And there is also the cost involved on removing and installing. I might have to tear up part of my Salon on my 54' to do this. Salon wood needs replacing so this might trigger the Salon renovation.

    Thats what I was trying to get feedback on the MDL3 as far as reliability etc. Unfortunately no many people have chimmed in.

    Thanks
  6. Caltexflanc

    Caltexflanc Senior Member

    Joined:
    Sep 25, 2011
    Messages:
    244
    Location:
    North Carolina
    I have an MDL4 with over 5400 hrs on it, basically a 4 cylinder version of the same engine (4A2.3 vs 3A1.7). We have basically beat the crap out of it for 6 years of our ownership, accounting for about 4000 of those hours. Just completely redid the cooling system, including both pumps, HEX, HEX cover and many many other parts. No problem sourcing them from Cummins distribution. The only part I hear is hard to get is the fuel lift pump, which people just replace with an electric pump.