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Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan Marine Generator


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  #31  
Old 01-28-2018, 04:03:15 PM
Vanman Vanman is online now
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Default Re: Onan Marine Generator

The nice thing about the marine water cooled exhaust manifold is that it will provide more free heat to use for space heating and domestic water heating.
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  #32  
Old 01-28-2018, 05:35:55 PM
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Default Re: Onan Marine Generator

Wow 5.7L engine for a 12.5Kw output . Should have no problem making power. Usually the only difficulty in converting a marine unit is how to make the fan work. Almost any car or truck rad will work to cool it . I have used mechanical and electric fans 12V and 120V. I would go with a 120V electric on that size of engine. Used multi speed furnace fans are easy to come by and flow lots of air.They are a bit bulky but quiet and reliable. Sealing the fan to rad with sheetmetal is important to get best effectiveness. To test the setup run the gen at full load till the temp is up to 180 deg plus then turn on the fan , the temps should drop over a couple of minutes even with a full load you should see it drop to below 160 deg. If it doesn't drop and keeps rising your cooling is insufficient. Cheers Dan
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  #33  
Old 01-29-2018, 12:31:22 AM
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Default Re: Onan Marine Generator

Thanks BigBlockChev,

I didn't see where this engine is 5.7L. Wow!

I was thinking I would go to the auto salvage and get a rad with a built-on fan and thermostat likely out of a mid-size car?
Do you think that would be big enough? I do have some furnace fans kicking around so that is an option.
I drained the coolant from the exhaust/heat exchanger and got out around 6 liters. I think with the engine included it holds around 9 liters. So I would like to get a rad with a similar capacity or what do you think?
Thanks.

It fired....
Just for curiosity I put together a fuel supply for the unit and hooked up a battery, warmed the plugs and pushed the start button.
It fired up before it even turned over once. I shut it down right away and I guess I will have to set up some kind of cooling system for it to be able to give it a proper test run.
Anyway, so far so good.

Hi BigBlockChev,

I was reading the manual and I think the engine size is 1.7 liters.
The engine oil capacity is 5.7 liters.
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  #34  
Old 01-29-2018, 05:18:57 AM
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Default Re: Onan Marine Generator

Viking66..

Here is a diagram of the cooling flow in the engine....
Any thoughts?
Thanks, Iver.
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  #35  
Old 01-29-2018, 04:43:09 PM
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Default Re: Onan Marine Generator

Another thing I have to contend with is a fuel tank. I was just thinking of a portable fuel tank from a boat but this engine requires a return line back to the tank as well and most tanks just have a fuel supply line only.
What have others done?
Thanks, Iver.
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  #36  
Old 01-30-2018, 08:02:08 PM
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Default Re: Onan Marine Generator

I have looked at the manual for this Genset. I would be interested in what's under that square cap where the T-Stat is located. I say this because it would be easy to hook up a Radiator using the upper and lower big hose connections. I would need to see what to do with the Bypass Passage connection.

Looks like you will need to use the Marine Exhaust Manifold as a search for that particular motor did not turn up much as far as parts go, very limited use by Onan/Cummins.

I am not positive if this is the engine on yours, but it looks very similar and is setup as a Land based type.

https://www.hso.dk/en/content/cummin...-diesel-engine

Good Luck with this one!!
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  #37  
Old 01-30-2018, 10:45:43 PM
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Default Re: Onan Marine Generator

on a conversion of this type marine engine would you need to route the coolant away from the exhaust manifolds?

I would think the radiator would have to be way oversized to remove the exhaust heat as well as engine heat.
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  #38  
Old 01-30-2018, 11:08:12 PM
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Default Re: Onan Marine Generator

The engine is putting out 24Hp so I don't think it's going to need a huge rad. My experience is with a 15.0MDJF and a Volkswagen golf diesel rad and fans , worked fine at full load! Being a diesel it is fairly efficient and does not produce a large excess of heat. I think that the heat scavenging from the exhaust is not near as much as many people believe. I am basing this on having mocked up and experimented with a number of different cooling setups on various marine engines to convert them to land based generators. You can hook up the water cooled exhaust if it suits you but I would not expect to be able to heat your house with it, possibly preheating a hot water tank, still useful but not the majority of your heating needs. Cheers Dan
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  #39  
Old 01-31-2018, 02:44:02 AM
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Default Re: Onan Marine Generator

Viking66

Thanks for the link.

That engine looks similar. Obviously newer. The starter setup is on the opposite side and mine doesn't have an alternator.

Also I was wondering about the bypass as well. Just plug it? Only used for the marine manifold. I think the square cap accommodates the t-stat and also allows for the bypass, the high coolant temp and low coolant level sensors.

I'll plan on using the marine manifold as a dry manifold and plug the heat exchanger lines.
Trial and error I guess.
Thanks, Iver.

Thanks BigBlockChev...

That's what I was thinking as well. Nice to hear you have already tried and experimented with this. Nothing better than someone who has more experience to get feedback.
I'll pick up a salvage rad with a built-on fan and temp sensor and try it out. I do have a temp gauge so I can monitor as needed.
Thanks again,
Iver.
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  #40  
Old 01-31-2018, 02:53:08 AM
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Default Re: Onan Marine Generator

Running a marine manifold dry, I wonder what is the likelihood of it cracking? Especially when first starting at very cold temperatures, when the cast iron is brittle. The inside quickly heats up and expands, while the outside remains below the brittle temperature?
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