Sealed cooling system

Engines, Shafts, Steering, Struts, Rudders, etc.
shelbygt
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Sealed cooling system

Postby shelbygt » Wed Sep 03, 2014 8:09 am

Wondering if there would be a good reason to have a sealed cooling system and how it works. I'm on freshwater/river. In such a system there must be a radiator to cool the water, just wondering where it would be located as the area where engine is located is covered. Also, how are the exhaust manifolds cooled?
1962 Marinette 31' Express
Single Gray Marine AMC 327

1955 Feathercraft Deluxe Runabout
Mercury 500

1976 Saquaro Jet Boat
Ford 460

Leviathon
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Re: Sealed cooling system

Postby Leviathon » Wed Sep 03, 2014 12:02 pm

If you go to my post called "Need an Engine" you will see a pic of a 318 with closed cooling. Where the manifold is connected to the riser portion, that gasket is solid - no holes. The coolant runs through the bottom portion of the manifold. The raw water cools the heated anti-freeze that is released via the thermosat in the engine to the blue tank mounted on the back of the engine, then exits out the riser portion of the manifold. Not sure what the advantages are except, my engine runs a little warmer which I think is good, and much easier to winterize. Just my thoughts.
Steve and Mary Levi
1973 32' Marinette Fisherman
Twin Chrysler 360's
El Ohssa
St. Joseph, Michigan

Fastjeff
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Re: Sealed cooling system

Postby Fastjeff » Wed Sep 03, 2014 3:44 pm

Any part NOT raw water cooled lasts a long time, so if the manifolds and risers are in the FWCooled circuit....

Jeff
"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington

jralbert
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Re: Sealed cooling system

Postby jralbert » Wed Sep 03, 2014 10:07 pm

One more shot at the comparison (and by the way, Jeff is correct)...

In raw water systems, seawater (fresh or brackish or salty) circulates in one continuous stream throughout the engine cooling system (manifolds/risers et al) and exits via the exhaust. The thermostat regulates the amount of the flow to keep temps constant. If it's salt water, which interacts with the metals of the engine parts , its is rather rough (corrosive) on the metals and you'll find yourself replacing costly parts more often. Scale and rust clog tiny ports. Fresh water much less so. Some folks flush after each use in salt water and prolong parts life. There are adapters to make this chore very easy.

Closed systems have two streams or channels. The water from these streams never intermixes. The closed stream is an anti-freeze mixture (usually 50/50) which is circulated around the engine past the hot surfaces, picking up heat and taking it to a heat exchanger (which the raw system doesn't have). That exchanger is the marine equivalent of an automobile radiator. Inside the exchanger, seawater runs through sealed tubing which is surrounded by the anti freeze stream. And that's where the heat exchange takes place. The relatively cool seawater soaks up the heat from the AF mix and runs out the exhausts. The AF mix now is a bit cooler and heads back to the engine to again carry away some heat.

The heat exchanger usually is mounted at the rear of the engine.

Maybe this diagram helps. The 8's are hoses or tubes carrying AF and the ooo's are raw water. --->>> is the stream direction for this (cheapo) graphic
______________________________________________
AF 8888888888888888888888888888----->>>
8888888888888888888888888888----->>>
raw <<<---ooooooooooooooooooooooo
<<<---ooooooooooooooooooooooo
AF 8888888888888888888888888888----->>>
8888888888888888888888888888----->>>

Hope this is helpful
-joel-
former owner 1988 '32 FB Sedan
Chesapeake Bay
twin 318 / 240 hp
Potomac MD

shelbygt
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Re: Sealed cooling system

Postby shelbygt » Thu Sep 04, 2014 2:32 am

Thank you for the replies! If the boat will only see freshwater I'm wondering if it would be worth it? What got me thinking about it is I'm considering putting an aluminum intake on cast iron AMC 327 and wondering if there would be an interaction between the two metals that antifreeze would help alleviate?

Maybe I'm confusing things but I'm thinking a closed system would provide a better way to introduce an anode ot some sort or maybe it wouldn't be necessary?
1962 Marinette 31' Express
Single Gray Marine AMC 327

1955 Feathercraft Deluxe Runabout
Mercury 500

1976 Saquaro Jet Boat
Ford 460

barkleydave
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Re: Sealed cooling system

Postby barkleydave » Thu Sep 04, 2014 7:29 am

Closed cooling is the way to go. MFG's used raw water cooling to keep costs lower and profits higher.

My next repower will be closed cooling!

Any boat that is used in salt closed is pretty much a must. Most do not flush raw systems after EVERY use and engines often are trashed in 5 years in FL.

safe boating,
dave
1987 Marinette 29 FB Sedan
Retired Boat Accident UL and USCG trained investigator
Retired USCG Captain

shelbygt
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Re: Sealed cooling system

Postby shelbygt » Thu Sep 04, 2014 10:23 am

barkleydave wrote:Closed cooling is the way to go. MFG's used raw water cooling to keep costs lower and profits higher.

My next repower will be closed cooling!

Any boat that is used in salt closed is pretty much a must. Most do not flush raw systems after EVERY use and engines often are trashed in 5 years in FL.

safe boating,
dave


Seems to me one could retro closed cooling to any engine. Even my old turd AMC 327. The water pump to serve an open and closed system would probably be the hard piece for mine but I'm guessing my pump could be modified. I'd like to find a diagram of how things flow.
1962 Marinette 31' Express
Single Gray Marine AMC 327

1955 Feathercraft Deluxe Runabout
Mercury 500

1976 Saquaro Jet Boat
Ford 460