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Onan Marine Radiator Conversion


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  #1  
Old 05-02-2011, 06:02:10 PM
jjayala jjayala is offline
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Default Onan Marine Radiator Conversion

Help!

I purchased a used Onan Marine Generator off Ebay hoping to use it for our mobile conession trailer. After taking it to Onan for a tune-up before using they tell me what I've purchased will not work and as this unit requires sea water to run through the heat exchanger! We are really stressed out as we are over budget and out of money and can't afford to buy another generator.

I've read one other post that these things can get converted to a radiator but no details. Is this something I can buy at Autozone and do myself?

Here are the details on my generator:

Model #: 7.5MDJE-3R/2268B,
Serial #: 0172347233
Voltage: 12/120/220,Single phase

Anything you can suggest, our business is at your mercy!

Cristina
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  #2  
Old 05-02-2011, 07:17:23 PM
Daverepair Daverepair is offline
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Default Re: Marine Radiator Conversion

look up a post called "my MDJF conversion" by bbuchorn dated 12-18-2010.
A MDJF is just a bigger version of what you have. It can be done but if you have a running MDJE you might be able to trade or sell for something like an RV type air cooled unit.
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  #3  
Old 05-02-2011, 07:27:15 PM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Marine Radiator Conversion

Just buy a radiator. Hook up your lower hose to the heat exchanger intake. Then hook up your upper hose to the outlet of the sea water pump. This will give you the same type of cooling system that you will find on a car. You will need to buy a cooling fan for the radiator.
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Old 05-02-2011, 08:17:33 PM
Dave Edmonds Dave Edmonds is offline
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Smile Re: Marine Radiator Conversion

Decision time - - -
If it's for a mobile concession trailer, it has to be mobile. What you have is heavy, and it will be heavier when full of coolant, along with a radiator, fan, etc. You will have to mount it on something to move it around.
What you have will take a fair amount of rigging to make it work. Billy's radiator is the first step, plus a fan, plus a battery, plus a fuel tank, plus a transportation method. But - - it can be made to work! There is a multitude of information on this website as to what it takes.
A vacu-flo air-cooled unit, mounted on a 2-wheel trailer, with a boat gas tank and a battery box, with a cover, makes an ideal "portable" source of power. I have three of these - they work well, and they are quiet! Went to a "festival" last Saturday, and the multitude of 3600-rpm "screamers" was deafening, except for one lone 1800 rpm unit that made almost no noise.
If your business is really at stake, you may need to take out a small loan and purchase a "screamer" that will keep you in business, then look for for a "cooler" way to make your power. What you have does have value, if you need to sell it or part it out.
Your mechanical abilities must be good if you intend to make what you have work. Liquid-cooled generators required circulated liquid to keep them cool, and making what you have operate properly in an environment it wasn't really designed for will take some work.
Just my thoughts - - -
Dave Edmonds
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Old 05-02-2011, 08:53:10 PM
bbuchorn bbuchorn is offline
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Default Re: Marine Radiator Conversion

Yes I did a marine conversion, and it works good, but it takes work to get to where you need to go. You have a diesel. 2 cylinder 7500 watt generator. A good one at that. How were you planning to fuel it? Me I got a trailer with a tank built in by pure dumb luck. I also have a gasoline powered 6.5 NHE R/V unit that would be way more appropriate for your use, but it is gasoline powered. I have it rigged for use with 6 gallon Boat tanks, with quick connects to remove some of the hazard of refueling.
For cooling your diesel unit you don't need the heat exchanger if you use a small car radiator and an electric fan from wally world. Where will you mount it?
you may be able to trade for an R/V unit that mounts in a small space, and can be set up with remote start etc.... In any case you have a project on your hands. I just wish you were closer so I could help you get it set up.
Lucky for you you have come to the right place for advice. These guys have a lot of valuable info and will help you to get where you need to go. Good luck and keep us posted. Oh- maybe some pictures of where you want to put the generator, along with pics of what you have, would help us help you.
The more we know of what you need the better advise we can give.
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Old 05-02-2011, 09:04:33 PM
Max Thompson Max Thompson is offline
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Default Re: Marine Radiator Conversion

Sounds like you need sell what you have, then run up to Toledo Oh. & pick up one of those 7.5 JBs for $400. That is likey less than you will spend start to finish cooling the marine set, not to mention the extra space it will take up.
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Old 05-02-2011, 11:21:26 PM
lijobi lijobi is offline
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Default Re: Marine Radiator Conversion

It can be done and it's relatively straight forward. These units weigh around 500lbs, so I wouldn't call them portable. Let me know if you have specific questions.
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Old 05-03-2011, 08:50:47 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Marine Radiator Conversion

Yes they are portable. If you have four guys and a crane. Good units but they are heavy.
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Old 10-30-2011, 06:30:16 PM
DieselCJ DieselCJ is offline
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Default Re: Marine Radiator Conversion

Quote:
Originally Posted by Billy J Shafer View Post
Just buy a radiator. Hook up your lower hose to the heat exchanger intake. Then hook up your upper hose to the outlet of the sea water pump. This will give you the same type of cooling system that you will find on a car. You will need to buy a cooling fan for the radiator.
I can get a marine 7.5KW for $600 locally, thinking about a radiator conversion and mounting it to a 4X4 trailer for backup-backup use. If your method will work this sounds fairly easy.

Is there a thermostat, or constant water flow? Did these units come with any sort of over-heat shut down?
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Old 10-30-2011, 07:45:14 PM
Gunny Gunny is offline
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Default Re: Marine Radiator Conversion

The internal cooling loop has the thermostat, no need for one in the radiator you'll install.

Yes, they have a high temperature shut down. Very IMPORTANT! this sensor has to be immersed in coolant or it won't work. It does not recognize steam as being hot.

Had a friend use a swimming pool to cool his MDJ during a power outage. Ran it for 2 weeks, water in the pool was nice and warm.
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