Seawater vs fresh water cooling in diesel engines: a truly basic question

[Ilanortho]

Please help resolve my confusion:
I have a Yanmar diesel
I get confused especially when considering winterizing is discussed.
I totally understand the concept and working of the heat exchanger

Where I get confused: when people talk about seawater and fresh water, does seawater refer to the external intake and discharge of cooling water for the heat ex-changer whereas freshwater refers to the on board sealed recirculating coolant with its antifreeze?

Thanks. Ilan

 

[woodster]

seawater refer to the external intake and discharge of cooling water for the heat ex-changer

sea or raw water

freshwater refers to the on board sealed recirculating coolant with its antifreeze?

fresh water

 

[Tally Ho]

That is the way I remember it.

I think you have it right.

Greg

 

[Ilanortho]

Thanks. Ilan
(Thanks; confusion arises because on Lake Michigan fresh water is all around me and sea water is the stuff everyone else sails on; when fresh water is mentioned by itself I always think of the lake and not the toxic fluid in my coolant system)

 

[centerline]

some people may describe it wrong when your hearing/reading it, so it can STILL be confusing.

raw water, sea water or open loop side....

engine coolant loop, freshwater loop or closed loop side

you will either have a raw water cooled, a freshwater cooled, or an air cooled engine...
these are all descriptive and easy to understand, but not always used.

 

[Ilanortho]

Thanks. Ilan

 

[Jackdaw]

This is confusing because the terms often used to describe the the two systems are not antonyms. Automatic or manual, open or closed, those words are pretty clear in their meaning and use. Indeed as others point out an open-loop system on the great lakes sounds much more like a fresh water system than the nasty green anti-freeze does.

I prefer to use an antonym pair:
Open-loop cooling, or
Close-loop cooling.

 

[markwbird]

Yes. You are correct. Seawater, raw water as it is sometime called is the water that is sucked in from outside, runs through the heat exchanger and out through the exhaust. The fresh water is that which is mixed with antifreeze and circulates through the engine in a closed loop.

 

[heritage]

This is confusing because the terms often used to describe the the two systems are not antonyms. Automatic or manual, open or closed, those words are pretty clear in their meaning and use. Indeed as others point out an open-loop system on the great lakes sounds much more like a fresh water system than the nasty green anti-freeze does.

I prefer to use an antonym pair:
Open-loop cooling, or
Close-loop cooling.

So, using your terminology, a Yanmar 3gm30F uses both open-loop cooling (raw water) and closed-loop cooling (coolant/fresh water mixture). And a 3gm30 uses only open-loop cooling (which could be fresh or salt water). I never heard it put that way, but it does get rid of the fresh water, salt water, confusion.

 

[Terry Cox]

As I recall our Yanmar Service manual refers to our system as "incapsulated". Whereby they describe the cooling system as having two separate parts shared only by a heat exchanger that provides a means of cooling by transferring heat from the closed-loop (incapsulated engine coolant/water mixture) side of the system with the open-loop (sea water) side.

Some boat manufacturers, for whatever reason, decided to dispense with the two separate systems and instead cool the inboard engine much like an outboard engine. Sea water is pumped into and through the engine and discharged back into the sea. Simple and less costly but more exposure to corrosive sea water.

I do not use the term "fresh water" for it is hardly fresh, or perhaps tap water would be more accurate. And sea water is water from the sea, bay, harbor, cove or whatever body of water that has no exposure to salt water. But then again I suppose someone will want to split more hairs with my hair splitting reply.

 

[Scott T-Bird]

It is confusing. On lakes, fresh water is on the outside. Besides, how can you call the coolant system "fresh water" if it is actually a mixture with chemical coolant?
I'd prefer to call the two systems "raw water loop" to describe the intake and "coolant system" to describe the closed loop. My 1GM has only "raw water cooling". My 2YM15 has a "coolant system". The raw water loop is simply understood and there is no need to state it.

 

[woodster]

And sea water is water from the sea, bay, harbor, cove or whatever body of water that has no exposure to salt water.

water that has no exposure to salt water

would this be called "sweetwater"

 

[Terry Cox]

would this be called "sweetwater"

Hi Woody, would not sweet water have nectar, fructose, honey, sugar, etc.? Just say'n.

 

[woodster]

Sweet water is what the old salts call it

 

[Jackdaw]

So, using your terminology, a Yanmar 3gm30F uses both open-loop cooling (raw water) and closed-loop cooling (coolant/fresh water mixture). And a 3gm30 uses only open-loop cooling (which could be fresh or salt water). I never heard it put that way, but it does get rid of the fresh water, salt water, confusion.

Sure. But even in the confusing example with two loops, there is only ONE cooling loop. So calling the COOLING loop open or closed always defines the system.

 

[Stu Jackson]

Sure. But even in the confusing example with two loops, there is only ONE cooling loop. So calling the COOLING loop open or closed always defines the system.

Yup, the RAW water is NOT a "loop" --- it comes in and goes out.

ONLY the coolant is a LOOP.

Loopie, I know.

Please stop thinking about the water OUTSIDE your boat.

Think about what your engine needs and is designed for.

 

[woodster]

Sure. But even in the confusing example with two loops, there is only ONE cooling loop. So calling the COOLING loop open or closed always defines the system.

back when mercruiser came out with the 0470 stern drive they touted it as the closed loop system