"[b]Ditto Henry's comment!
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Ditto Henry's comment! He is correct about the E/G!
Before chastising me for this, hear me out please!
Somewhere in the mix years ago, the ethylene glycol engine heat exchanger systems became known as "Fresh Water Cooling". Perhaps this occurred during the advent of what I call, a "Closed Cooling System", whereby salt water boats were being fitted with these to protect the engine not only from freeze damage, but for eliminating salt water corrosion and extending the life of the engine block and cylinder heads!
To me, the term
"Fresh Water Cooling" (one of my little pet peeves) is a misnomer at best! Believe me.... there is nothing fresh about Ethylene Glycol and H2O...
Ya can't drink it... ya can't bath in it!
But the industry ran with it!
So, whether correct or not, I always refer to these as a "Closed Cooling system" or a "Closed System". (yes, I'm anal about this)
As for thermostat rating...... any open, or "raw water cooling" system that is in salt water must run the cooler 145* stat. This is due to salt crystallization that occurs when temps exceed this heat range. This crystallization adds to the build up of corrosion on the internal cooling jackets of cast iron engines and exhaust system, and eventually limits the ability for heat transfer.
So this crystallization is a concern in this area as well.
I'd recommend keeping the temps low if in salt water. Most good and thorough OEM manuals will give this recommendation as well.
Conversely, any open system that is used in lake, river or so called "fresh water" can use the warmer 160* and/or 180* stat. Engines prefer this temperature over the cooler temps.
I'd recommend running the warmer stats if you are
not in salt water!
Any "Closed System" will be best if you keep engine temps between 160* + and 180*.
Circ pump: The engine's "Circ" pump (the belt driven factory engine pump) is still using the same HP to operate this pump, whether the system is a "Closed Cooling System" or a "Raw Water Cooling" system..... the engine load is the same.
IOW's, Both systems use the Circ pump for circulating the coolant through the engine.... whether the coolant is E/G or river/lake/sea water.
So neither has a benefit over the other in regards to this, IMO!
Now we factor in what Henry just tossed in the mix, and it only makes sense to stay with a closed system if it already exists.
Personally, I'd like to see ALL BOATS equipped with a closed system.
The draw-back would be, the shops would not be replacing engine$ in the $pring time!
Side note: Should you remove the "Closed Cooling" system, this engine circ pump now needs to be replaced with a marine version that has a different shaft seal AND has the bronze impeller.
The sea or raw water pump can likely remain the same.
A tip for some:
Pull your raw water pump impellers for the winter, and leave your drives fully DOWN for the duration as to protect your drive bellows.... you will extend the life of them.
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