Onan marine genset

Discussion in 'Off Grid Living' started by Airtime, Nov 18, 2014.


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  1. Airtime

    Airtime Monkey+++ Site Supporter

    Anyone have any experience and knowledge with the marine Onan MDJC (4 cylinder, 12k watt) with YD brushless generator? Anything you know of reputation history etc.? This is a model from back in the early-mid 80's. Thanks.

    AT
     
  2. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    sec_monkey likes this.
  3. Dunerunner

    Dunerunner Monkey

    Well, here is a link to a parts list. http://www.cumminsonan.com/www/pdf/marine/f-1229.pdf

    Service Manual here - http://www.cumminsonan.com/www/pdf/manuals/974-0750.pdf

    This was a Marine Diesel engine, which probably means they utilized sea water for cooling. Since it is a marine engine, it was designed for this duty. It should perform just fine with a radiator and antifreeze/water mix coolant. I would want to run it and check the generator output under load before buying it. If you already own it, how do you intend to use it and are you in a position to run it and see if it works?

    The 12KW "Gas" Onan on my RV is air cooled and has been a gem for 14 years of service. Had the carb rebuilt once, but that was my fault. The generator section is identical to your gen set.
     
    sec_monkey likes this.
  4. Maxflax

    Maxflax Lightning in a bottle

    I bought this one this year to power a huge wood bandsaw (50 amp 220) for my biz. It cost less than rewiring the house, and we'll be selling soon so it was the better move. In spite of being near 500 lbs it was a one man operation to assemble it, and in my limited use of it I'm very pleased. It's a gas powered V Twin. It will be an initial temporary and later a backup Castle generator

    Generac Power Systems | Portable Generator | GP Series | GP17500E | Generac Power Systems
     
  5. BTPost

    BTPost Old Fart Snow Monkey Moderator

    I can provide ANY, and ALL Manuals for ANY and ALL Onan Gensets.... I have extensive experience with J Series Onan Gensets, like the one @Airtime is asking about. (MDJC) They are PERFECT for a Backup Power/Heat Generator, as they lend themselves to CoGeneration just as they are. Have questions, Ask away....
     
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  6. Maxflax

    Maxflax Lightning in a bottle

    BT, I do have a question: Can these diesel units be tuned to run on wood alky?
     
  7. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Diesel Engines can be made to run on, dang near ANYTHING, that will flow thru the Fuel Filters.... The trick is to know the BTU content of the Fuel, and to understand the viscosity of the fuel, to be used. If Wood Alcohol was my "Fuel of Choice" I would cut it 50:50 with some kind of thicker fuel, like almost ANYTHING, from ANY Grade of Diesel, to Veggie Oil, to bring up the viscosity, to close to what the Injection Pump was designed for. That will alleviate many of the issues with such a Low Viscosity Main Fuel. The MAIN thing that you MUST Remember in Diesel Fuel, is that, "It MUST be absolutely CLEAN, and Absolutely NO WATER, in it." Particulates, and, or, Water, will kill and Injection Pump, and or Injectors, faster that ANYTHING on Earth. 2 Micron Primary Fuel Filter, and NO Water, is critical...
     
  8. Maxflax

    Maxflax Lightning in a bottle

    Thanks BT, I hoped it was a go but it's always good to hear from them who flunk the chunk. I have near unlimited heavy timber and there will be a LOT of waste from the future light thinning ops. We'll kiln dry and sell or use the timber for my new woodworking biz, the rest is firewood or could be wood alky
     
  9. BTPost

    BTPost Old Fart Snow Monkey Moderator

    I was thinking about the concrete flooring, you plan to use in the Castle..... If one put PEX Tubing down, before the Floor Pour, it could be used as a Radiator, for any Liquid Cooled Genset, that one might install for Backup, or Primary Power. Making use of the Cooling and Exhaust BTPs, rather than throwing them away, by heating the "Out of Doors" makes little sense, since you already paid for those BTUs when you bought the fuel. Rule of Thumb that applies is, 1/3 of the BTUs goes out the Electrical Connection, 1/3 of them "Go up the Stack" and 1/3 of them go out the Radiator. Pumping them into the Concrete Flooring, especially if you have a backup Wood Burning Boiler, for when the Genset isn't running, just make a Ton of Sense, If you were smart enough to install the PEX Tubing, during construction... Trying to do so After, is a Fools Errand...
     
    Last edited: Nov 18, 2014
  10. Dunerunner

    Dunerunner Monkey

    I didn't think about scavenging the waste heat from the cooling system to heat the house/shop/cabin, etc....
     
  11. Maxflax

    Maxflax Lightning in a bottle


    I considered it, but it's costly, the basement burner will heat the entire place, It's commercial-huge :eek: and also we will have floor registers and fan blowers on the chimney on each floor, and what's left of heat will heat the huge battlement growing hothouse. I am going to install tubes in the log burner, for hot water for the baths, including a huge sunken granite slab hot tub. Later on the pool house build will have a similar setup

    Also, I'll have unlimited wood
     
  12. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    If you do change your mind an use radiant heat from the floor, make sure to fully hydro test the install before and after the floor pour. Best would be a three circuit layout in case one loop develops a leak in the future. That said, you will LIKE hydroponic heating, but not cooling if using the same pipe loops. Also, use a reverse return setup to limit colder floors, plus the loops would be self balancing and save a bunch of circuit setter loop balance valving.
     
    Maxflax likes this.
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