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Onan MDJE 7.5 Change to home generator


I got a new generator for my boat.
I want to convert my old generator for home use.
I would like to set it up with a radiator & fan instead of raw water cooling.
My raw water pump has started leaking a lot so it seems that it would be better to convert it to a radiator at this point.Anyone know where to get the parts I will need to do this?
The specs are;
model 7.5
ac volts 120/240
phase 1
kva 7.5
watts 7500
pf 1
amps 31.3
cy 60
rpm 1800
bat 12volt


Billy J Shafer

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Re: MDJE 7.5 Change to home generator

There is no kit for doing that. You just have to look around for what fits your needs. I assume you have a closed cooling system. If not you will need a water pump of some kind. Junk yard would be a god source for a radiator. You just have to look.


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If you have a closed cooling system you can use the freshwater pump and replace the heat exchanger with a radiator. The wet exhaust will have to get converted to a regular one unless you want to use a bunch of water.


Has anyone made this conversion?
Does anyone have the radiator / fan / or fan shroud they would like to sell?


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I've done it, as have a few others on here.

I don't think there is any standard radiator setup to buy since it is marine engine.

I removed the raw water pump and am running the engine cooling pump into a Modine heater. I like this because it has it's own fan, and it runs on 120 volts. Others have set up an old car radiatr with a belt driven fan; this seemed more complex to me. It would probably be better if you are mounting the generator on a trailer.

Also, I ran the cooling lines into my garage, and hung the Modine from the ceiling. So while I am making electricity, I'm heating the garage too.


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I used a VW diesel rad and fan/shroud setup for my 15KW mdjf. works fine. I left the heat exchanger in place to use for preheating water if I get so inclined. I took out the raw water pump guts and made a block plate to cover. Cheers Dan


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My uncle also has the same genny, and has diverted the heat to his house - it's not a lot, but no point warming the sparrows, eh?
He (I, directed by him, he's an old fella) is also going to direct the heat from his river barge longboat thing's engine into the bridge - has a little wood/oil stove which keeps the lounge warm, but on those long journeys which I do in my speedboat in 5 minutes, he has to stand up there in the unheated bridge. for an hour or more. Maybe my boat is too fast, maybe his is too slow - but I've towed it off a sandbar once (backwards) and a 13ft Fletcher with a 50hp Yamaha outboard takes a LONG time to drag a 25 tonne boat.
I think my engine is too small, best step up to an old Mercury I6 150...