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TOPIC: Full closed cooling or no?

Full closed cooling or no? 31 Aug 2017 16:01 #1

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Cant quite determin if this is a full or partial system. What do you think?

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1993 formula pc 31 twin 454 bravo 2
1989 2655 cierra 5.7 omc cobra
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Anchor bay clinton river
Michigan

Full closed cooling or no? 31 Aug 2017 16:08 #2

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It appears to be a full closed system. Are the two hoses coming off the t-stat housing going to the exhaust manifolds? If so then full system.

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1997 Maxum 2400 SCR 5.7LX Bravo II

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Full closed cooling or no? 31 Aug 2017 16:40 #3

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Mike, It looks to have Mercruisers SS exhaust elbows but I can't see if there's a raw water hose feeding them or not. If they're capped off then she's part closed.
Post a pic of the exhaust: manifold, spacer, elbow and the hose connections to them.

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Full closed cooling or no? 31 Aug 2017 16:43 #4

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Dave in the first picture there is a hose coming off the HE that splits and goes to the elbows which should be raw water. In the last picture there are two hoses coming off the t-stat and two on the backside of the HE which appears to be closed cooling for the exhaust manifolds.

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1997 Maxum 2400 SCR 5.7LX Bravo II

Mike

Full closed cooling or no? 31 Aug 2017 16:54 #5

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ive been messing about with boats for many years, and I suppose its time for someone to enlighten me about the "partial" closed loop cooling system. I have never heard of such a thing or how it would work. maybe it means a closed loop cooling system with dry exhaust?...

you have a heat exchanger, so in my opinion you have a closed loop cooling system.... you should see fresh water and coolant under the cap of the heat exchanger that flows around the outside the tubes of the heat exchanger, and then out in a loop thru the motor, circulated by the engine water pump. at the same time, sea water is picked up by the impeller in the lower unit and sent to the heat exchanger where it passes thru the tubes inside the heat exchanger, and then dumped into the water jacketed exhaust manifolds to cool them as both the exhaust gases and the water flow up and over the riser elbows where they now mix together and exit thru the outdrive...

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Full closed cooling or no? 31 Aug 2017 17:03 #6

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Centerline2 wrote: ive been messing about with boats for many years, and I suppose its time for someone to enlighten me about the "partial" closed loop cooling system. I have never heard of such a thing or how it would work. maybe it means a closed loop cooling system with dry exhaust?...

you have a heat exchanger, so in my opinion you have a closed loop cooling system.... you should see fresh water and coolant under the cap of the heat exchanger that flows around the outside the tubes of the heat exchanger, and then out in a loop thru the motor, circulated by the engine water pump. at the same time, sea water is picked up by the impeller in the lower unit and sent to the heat exchanger where it passes thru the tubes inside the heat exchanger, and then dumped into the water jacketed exhaust manifolds to cool them as both the exhaust gases and the water flow up and over the riser elbows where they now mix together and exit thru the outdrive...


A "Full" closed cooling system circulates coolant through the engine and exhaust manifold and he elbows are raw water cooled. As you said raw water is also circulated through the HE to remove heat from the closed cooling.
A "Partial or half" closed cooling system circulates coolant through the engine only and the exhaust manifold and elbow are raw water cooled.
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1997 Maxum 2400 SCR 5.7LX Bravo II

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Full closed cooling or no? 31 Aug 2017 17:09 #7

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Centerline2 wrote: ive been messing about with boats for many years, and I suppose its time for someone to enlighten me about the "partial" closed loop cooling system. I have never heard of such a thing or how it would work. maybe it means a closed loop cooling system with dry exhaust?...

you have a heat exchanger, so in my opinion you have a closed loop cooling system.... you should see fresh water and coolant under the cap of the heat exchanger that flows around the outside the tubes of the heat exchanger, and then out in a loop thru the motor, circulated by the engine water pump. at the same time, sea water is picked up by the impeller in the lower unit and sent to the heat exchanger where it passes thru the tubes inside the heat exchanger, and then dumped into the water jacketed exhaust manifolds to cool them as both the exhaust gases and the water flow up and over the riser elbows where they now mix together and exit thru the outdrive...


They are often referred to as a half vs a full fresh water cooling systems. A half system runs raw water through the exhaust manifolds up to the risers and overboard. A full system runs coolant through the manifolds. The risers still get raw water and this goes overboard. The advantage of a full system is that manifolds last much longer.
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Full closed cooling or no? 31 Aug 2017 17:17 #8

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That is a full closed system

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Full closed cooling or no? 31 Aug 2017 17:20 #9

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If you have trouble following the hoses the easiest way to see is crack open a plug on the manifold ( not the riser) and see what comes out. If its antifreeze it's full closed. Of course that's assuming you have antifreeze in the block.

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1989 Avanti 3450 Sunbridge twin 454's

1979 Bayliner Conquest 3150 hull#23

1979 Bayliner Conquest 3150 hardtop hull#24
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Full closed cooling or no? 31 Aug 2017 17:33 #10

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FULL,
Man, that is tight in there!
PORT side starter never goes out hopefully... don't even want to think about replacing that :)

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Full closed cooling or no? 01 Sep 2017 03:23 #11

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Norton Rider wrote:
A half system runs raw water through the exhaust manifolds up to the risers and overboard. A full system runs coolant through the manifolds. The risers still get raw water and this goes overboard. The advantage of a full system is that manifolds last much longer.


so most older boats with a "closed" loop cooling system must be really a half system? because the raw water goes in the front of the manifolds and out over the top of the risers... i can see the advantage of running coolant thru the manifolds, so what does it take to convert a half system to a full system? and does it cool as efficiently?.. thanks

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Full closed cooling or no? 01 Sep 2017 10:57 #12

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I will get more pics tonight. If I recall one of the tubes off the risers run to the heat exchanger. Which is deceptive because that doesnt mean its coolant, that could still be raw water from the outer jacket, routed to exit through the exhaust.

The raw water pump is belt driven, these are bravo 2's.

Yes its insane how tight it is, not looking forward to doing anything down there, am pulling engines for rebuild this winter.

Difference between half and full is as stated, exhaust manis are still raw water cooled. What confuses me is in a full, there is a plate that blocks the jackets from the risers.

Unless my terminology on what parts what on an exhaust system is wrong, why do they sell full aluminum kits if the riser still gets raw water through it?

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1993 formula pc 31 twin 454 bravo 2
1989 2655 cierra 5.7 omc cobra
2014 "searay" tandom trailer

Anchor bay clinton river
Michigan
Last Edit: by businessgetmoney.

Full closed cooling or no? 01 Sep 2017 11:04 #13

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As well this boat has strainers in the bilge for the raw water pick up. Idk if this is factory or not.

If I understand correctly: Ive read of people modding this to avoid sucking up muck the drives churn up. From here they would cutt the raw water tube outside in the transom assembly for the drives and do a block off from the belt driven pump that would feed the drives? Idk that system confuses me. And honestly these strainers have been a pain, everytime i leave my slip in the canal they get clogged. Last time i didnt wven make it out of the river and had to go diving to clear the scuppers. I would way rather lift the drives and lay on the playform and remove debris. Wish there was some back flush valves for the strainers

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1993 formula pc 31 twin 454 bravo 2
1989 2655 cierra 5.7 omc cobra
2014 "searay" tandom trailer

Anchor bay clinton river
Michigan

Full closed cooling or no? 01 Sep 2017 12:02 #14

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Centerline2 wrote:

Norton Rider wrote:
A half system runs raw water through the exhaust manifolds up to the risers and overboard. A full system runs coolant through the manifolds. The risers still get raw water and this goes overboard. The advantage of a full system is that manifolds last much longer.


so most older boats with a "closed" loop cooling system must be really a half system? because the raw water goes in the front of the manifolds and out over the top of the risers... i can see the advantage of running coolant thru the manifolds, so what does it take to convert a half system to a full system? and does it cool as efficiently?.. thanks


A larger HE that is sized to cool both the engine and manifolds plus the hoses to the manifolds and block off gaskets between manifolds and elbows.

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1997 Maxum 2400 SCR 5.7LX Bravo II

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Full closed cooling or no? 01 Sep 2017 12:08 #15

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businessgetmoney wrote: As well this boat has strainers in the bilge for the raw water pick up. Idk if this is factory or not.

If I understand correctly: Ive read of people modding this to avoid sucking up muck the drives churn up. From here they would cutt the raw water tube outside in the transom assembly for the drives and do a block off from the belt driven pump that would feed the drives? Idk that system confuses me. And honestly these strainers have been a pain, everytime i leave my slip in the canal they get clogged. Last time i didnt wven make it out of the river and had to go diving to clear the scuppers. I would way rather lift the drives and lay on the playform and remove debris. Wish there was some back flush valves for the strainers


Are the strainers connected to the hose from the drive or to the thru hull next to it in the first picture? Some use blockoff kits on the inner transom assembly so the raw water doesn't come from the drive but a thru hull.

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1997 Maxum 2400 SCR 5.7LX Bravo II

Mike

Full closed cooling or no? 01 Sep 2017 12:15 #16

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The strainers are connected to the through hull and feed the belt pump for raw water. It looks factory but who knows.

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1993 formula pc 31 twin 454 bravo 2
1989 2655 cierra 5.7 omc cobra
2014 "searay" tandom trailer

Anchor bay clinton river
Michigan

Full closed cooling or no? 01 Sep 2017 12:33 #17

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Centerline2 wrote: I've been messing about with boats for many years, and I suppose its time for someone to enlighten me about the "partial" closed loop cooling system. I have never heard of such a thing or how it would work.
That would be what is referred to as a "Half Closed Cooling System". As noted, the cylinder block and cylinder heads only are E/G cooled.

maybe it means a closed loop cooling system with dry exhaust?...
No dry exhaust on our cruiser boats.

you have a heat exchanger, so in my opinion you have a closed loop cooling system....
Correct...... know as a Closed Cooling System!
(the term "Fresh Water Cooling" is a misnomer)


you should see fresh water and coolant under the cap of the heat exchanger
Incorrect! You will see an Ethylene Glycol and distilled H2O mixture ONLY.

that flows around the outside the tubes of the heat exchanger, and then out in a loop thru the Engine, circulated by the engine coolant circulating pump.
Yes!

at the same time, sea water is picked up by the impeller in the lower unit (yes......., or by the engine located seawater pump) and sent to the heat exchanger where it passes thru the tubes inside the heat exchanger,
Yes, that is called the "tube bundle".

and then dumped into the water jacketed exhaust manifolds to cool them
On a "Half System"..... yes!

as both the exhaust gases and the water flow up and over the elbows where they now mix together and exit thru the outdrive...
Yes..... either that or it exits via a thru-hull exhaust system.



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Rick E. Portland, Oregon
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