Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

oregonrafter

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I'm going to install a closed cooling system on a Mercruiser 4.3 Vortec with an alpha 1 drive. The motor does not currently have a seawater pump, except for the one in the outdrive. Do I need a separate belt-driven seawater pump in addition to the impeller that is installed in the Alpha 1 drive? -It seems redundant to have two pumps working on the same water supply line.

Thanks,
Mike
 
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Bondo

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

I'm going to install a closed cooling system on a Mercruiser 4.3 Vortec with an alpha 1 drive. The motor does not currently have a seawater pump, except for the one in the outdrive. Do I need a separate belt-driven seawater pump in addition to the impeller that is installed in the Alpha 1 drive? -It seems redundant to have two pumps working on the same water supply line.

Thanks,
Mike

Ayuh,.... Welcome Aboard,.... Is this a Brand New motor,..??

If not, has it ever been run in the Brine,..??

Old motors with salt in 'em, Ain't a candidate for closed coolin',... It won't work,...

Otherwise, yer Right, ya only run 1 impeller pump,...
The Alpha's pump would just pump through the drive, 'n out the hose ya cut off,...
A motor mounted raw water pump would be plumbed into yer new system,...
 

oregonrafter

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

Ayuh,.... Welcome Aboard,.... Is this a Brand New motor,..??

If not, has it ever been run in the Brine,..??

Old motors with salt in 'em, Ain't a candidate for closed coolin',... It won't work,...

Otherwise, yer Right, ya only run 1 impeller pump,...
The Alpha's pump would just pump through the drive, 'n out the hose ya cut off,...
A motor mounted raw water pump would be plumbed into yer new system,...
The "new" motor is used, but it only has about 200 hours of freshwater use.

OK, so I don't need a belt-driven water pump if I'm using the water pump on the outdrive?
 

MarkSee

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

OK, so I don't need a belt-driven water pump if I'm using the water pump on the outdrive?

No, you DO need a belt driven pump to supply the water to the engine/exchanger and you'll cut the hose at the drive.
There's a special procedure to do this conversion along with needing some type of pickup or thru-hull fitting as the new water supply.
Here's a link where BD references this and I'm sure a little digging and you'll find the exact procedure:

http://forums.iboats.com/mercruiser...ruiser-260-pre-alpha-cooling-hose-447438.html

Mark
 

thumpar

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

It is not recommended to convert a motor with over 20 hours on it.
 

achris

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

It is not recommended to convert a motor with over 20 hours on it.

Only if that 20 hours is salt-water. If the engine has only ever been run in fresh, and there's no appreciable rust in the block, closed cooling is ok...
 

oregonrafter

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

No, you DO need a belt driven pump to supply the water to the engine/exchanger and you'll cut the hose at the drive.
There's a special procedure to do this conversion along with needing some type of pickup or thru-hull fitting as the new water supply.
Here's a link where BD references this and I'm sure a little digging and you'll find the exact procedure:

http://forums.iboats.com/mercruiser...ruiser-260-pre-alpha-cooling-hose-447438.html

Mark
Thanks fo r your reply, Mark. Though I understand what you're telling me, I don't understand why. If there is already a pump in the outdrive that supplies raw water to the engine, why do I need to "delete" this pump, and install another belt-driven pump on the engine?
 

dan t.

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

It depends on how cold the water is that you are running in. I run full closed cooling on a Merc 350 Magnum with just the pump in the leg, it never goes above 180 no matter how hard it is worked. If you are running in a lake with bathtub water you might want a seperate raw water pump
 

oregonrafter

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

Only if that 20 hours is salt-water. If the engine has only ever been run in fresh, and there's no appreciable rust in the block, closed cooling is ok...
So, the issue with converting a saltwater-cooled engine, is that rust will flake-off and clog the circulation?
 

oregonrafter

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

It depends on how cold the water is that you are running in. I run full closed cooling on a Merc 350 Magnum with just the pump in the leg, it never goes above 180 no matter how hard it is worked. If you are running in a lake with bathtub water you might want a seperate raw water pump
I'm in northern Oregon, and this boat will be used mainly offshore, and also in the Columbia river. The ocean does not typically get above 63 degrees here, and the river doesn't usually go above 65 degrees, or so. There are no "bathtubs" here. :)
 

dan t.

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

Is your drive an Alpha 1 or a Alpha 1 gen II, the gen II like I have has a much higher capacity water pump that seems to be quite adiquate when running in cold water. The original Alpha 1 pump is a little short on volume for a full closed system.
 

oregonrafter

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

It's an Alpha 1, not an Alpha 1 gen 2.

I want to clarify that this is going to be a half cooling system (engine only) and not a full cooling system (engine and manifolds). With this in mind, do you think the Alpha 1 impeller will be enough to supply raw water?
 

oregonrafter

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

It's an Alpha 1, not an Alpha 1 gen 2.

I want to clarify that this is going to be a half cooling system (engine only) and not a full cooling system (engine and manifolds). With this in mind, do you think the Alpha 1 impeller will be enough to supply raw water?
Still looking for suggestions on this question.
 

achris

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

Where are you buying the kit from? They should be able to answer that question, as it's specific to the kit... But you also need to be aware that putting any form of closed cooling on an engine more than 1 year or 20 hours old is a bad idea....

Chris.....
 

oregonrafter

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

Where are you buying the kit from? They should be able to answer that question, as it's specific to the kit... But you also need to be aware that putting any form of closed cooling on an engine more than 1 year or 20 hours old is a bad idea....

Chris.....
Chris, your post (#6) is applicable here, unless you've changed your mind about what you said earlier. This is a freshwater (only) engine.

The heat exchanger is made by San Juan Engineering, but it is used, so I can't really get advice from them. Besides, they are a wholesaler, and their contact info is not readily available.
 

achris

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Re: Mercruiser 4.3 vortec fresh water cooling - Need seawater / raw water pump?

Quite right. Fresh water is a whole different issue. Just saw your name as "Oregon" and assumed Pacific... :facepalm:

I believe San Juan customer service is very good...

Just ring them and ask, as an inquiry, about putting a half system on an Alpha One... See what they say.

Chris....
 
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