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Old 28-05-2011, 13:02   #1
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Do Marine Diesel Engines Run Cooler Than Vehicle Equivalents

I always thought that marine engine such as a Perkins 4236 (indirect cooled via a heat exchanger) ran cooler than the vehicle model.

My understanding was that the road version burned hotter to help with exhaust gas flow but that the marine versions burned cooler to prevent deposits building up in the exhaust.

Now by burn I dont mean the temperature of the flame front or ignition point but the block temperature.

I am asking because an associate has a dilemma, he does not know what thermostat to put into the fresh water circuit. I suggested that it would be cooler than than the vehicle one i.e. open earlier. I dont know the engine type just that its a Yanmar.

Am I right or wrong or does it depend?

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BlowingOldBoots
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Old 28-05-2011, 13:03   #2
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Re: Do Marine Diesel Engines Run Cooler Than Vehicle Equivalents

They both run at whatever the thermostat is set at!
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Old 28-05-2011, 13:18   #3
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Re: Do Marine Diesel Engines Run Cooler Than Vehicle Equivalents

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Originally Posted by capngeo View Post
They both run at whatever the thermostat is set at!
Obviously, but the examples I gave are what I thought were the reasons for the thermostats having different opening temperature settings between the road and marine versions.

Actually maybe its more to do with the sea water flow rate through the heat exchanger and a lot less to do with the point that the thermostat opens.

Anyway , the basic question is does the block run cooler?
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Old 28-05-2011, 13:33   #4
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I'm going with the operating temp the engine was designed for.friend needs to call yanmar.but usually 180
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Old 28-05-2011, 13:58   #5
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Re: Do Marine Diesel Engines Run Cooler Than Vehicle Equivalents

Sorry... had a wise-ass moment!
My understanding is that 180° is optimal for a diesel that IS NOT subject to Draconian air pollution laws. MOST industrial (Marine included) Diesels are close to that. The automotive diesels seem to be run at closer to 200° presumably for pollution controls. I'm sure Gord will have a link along in a moment or two that confirms/refutes my post.
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Old 28-05-2011, 14:27   #6
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Re: Do Marine Diesel Engines Run Cooler Than Vehicle Equivalents

I think boat engines would run cooler, and my Universal manual specifies a 160 degree F thermostat that is 20 degrees lower than the typical thermostat for the Kubota it is based on. Certainly, generally speaking, the benefit of a hotter engine would be higher fuel economy with a tradeoff of lower durability. Sailboat owners would care less about the former and more about the latter. Nothing is cast in stone, but I see little evidence to the contrary.
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Old 28-05-2011, 14:31   #7
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Re: Do Marine Diesel Engines Run Cooler Than Vehicle Equivalents

Four stroke outboards are running hotter in order to burn cleaner. The trade off is that salt water is causing them to corrode out quicker. We had a pair of Suzuki's at work that have reached the end of their relatively short lives because of this. This was explained to me by the mechanic who works on them.

Don't think it is necessary to be concerned about the internal temperature for Diesels. The engineers who designed them know what they are doing.
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Old 28-05-2011, 15:07   #8
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Re: Do Marine Diesel Engines Run Cooler Than Vehicle Equivalents

My Yanmar 3GMY30F runs at 180 degrees. This is a closed system with a heat exchanger and coolant. Coincidently, this was confirmed by a reliable source - last week's Deadliest Catch TV show!

The temperature is lower for seawater cooled diesels.
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