Retrofitting Mercruiser Closed cooling V8s

tank1949

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I am examining all of my options. I have found a couple of closed cooling systems to retro-fit an Alpha V8 where sea water comes up through the OD and into the heat exchanger to cool down antifreeze that passes through the block. The kit does not require an external water pump/pick up. It relies solely on the ODs pickup water pump, but I am sure the motor's circulating pump assists. The kit's information was not specific if it also passed antifreeze through the exhaust manifolds. I prefer to purchase kit where the risers would be the only IRON passing sea water.

Would one of these type kits work sufficiently, even cooling down exhaust manifolds? Most I have seen work from a dedicated pump like on Bravo drives.

I realize that I most likely would clog a heat exchanger, if the motor had experienced a lot of salt water over time. But, I may replace motors too or buy a fresh water boat.


Any suggestions!
 

Scott Danforth

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kits for the Alpha drive are half system only (block and heads). exhaust is still raw water cooled. it is because the Alpha raw water pump can only move so much water.

Bravo systems are generally full systems (Block, Heads, and Exhaust)

The engine circulation pump still circulates within the block and heads.

generally the cost and head ache is not worth it on a motor that has already seen salt water
 

alldodge

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If your not rebuilding the motor, don't put closed cooling on it of any kind
 

tpenfield

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I put a FULL closed cooling system on both of my Mercruisers (twins), but they are Bravo drives. As stated, the condition of the engine's water paasages are important as a significant amount of scaling/metal flake, etc can block the heat exchanger and lead to problems later on.

The HALF systems do not need quite as much flow, and are the common route for Alpha drives. You could always put in a sea water pump running off the engine in order to get a Full system with confidence.

Which brand of system are you looking at? SeaKamp or San Jaun Engineering ?

I installed the San Jaun kits, of which I have a thread here on iBoats that you can search and see. Installing the kits is about a 7 on a 10 scale, so . . . not easy, but not impossible.

BTW - the recirculating pump has and will have nothing to do with the water intake, it will only run the 'closed' side of the system.
 
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tank1949

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I put a FULL closed cooling system on both of my Mercruisers (twins), but they are Bravo drives. As stated, the condition of the engine's water paasages are important as a significant amount of scaling/metal flake, etc can block the heat exchanger and lead to problems later on.

The HALF systems do not need quite as much flow, and are the common route for Alpha drives. You could always put in a sea water pump running off the engine in order to get a Full system with confidence.

Which brand of system are you looking at? SeaKamp or San Jaun Engineering ?

I installed the San Jaun kits, of which I have a thread here on iBoats that you can search and see. Installing the kits is about a 7 on a 10 scale, so . . . not easy, but not impossible.

BTW - the recirculating pump has and will have nothing to do with the water intake, it will only run the 'closed' side of the system.

Thx to all. I am examining all options. Sounds like if I add new motors or buy fresh water boat and add kit with additional pump, this would be my best option. I'd want full system to minimize future iron replacement costs. Down here in Florida, about 5-6 years is all we get out of risers, even if we constantly flush with fresh water after every trip. The kits that I have examined appear to be in the 1200-1500 $$ range. If you have preference???
 

alldodge

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add new motors or buy fresh water boat

You can convert with new or newly rebuilt motors, but it is not recommended to convert a fresh water boat with much more then 20 hours. Even fresh water bats get build up. Even with a full closed system, the risers will be slat water cooled.
 

tank1949

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kits for the Alpha drive are half system only (block and heads). exhaust is still raw water cooled. it is because the Alpha raw water pump can only move so much water.

Bravo systems are generally full systems (Block, Heads, and Exhaust)

The engine circulation pump still circulates within the block and heads.

generally the cost and head ache is not worth it on a motor that has already seen salt water

I realize that taking an existing MC cast iron block, that has experienced repeated use in salt water, and converting its cooling system to a closed one is not a good idea, because the heat exchanger most probably will clog up with rust. What if the motor had only been used in fresh water like one of the Great Lakes?
 

HT32BSX115

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I realize that taking an existing MC cast iron block, that has experienced repeated use in salt water, and converting its cooling system to a closed one is not a good idea, because the heat exchanger most probably will clog up with rust. What if the motor had only been used in fresh water like one of the Great Lakes?

Howdy,

I bought my 1997 Mercruiser 454/Bravo in 2006 to replace the 1987 460 King Kobra in my FourWinns 211 LIberator............... It had 122 NON-salt water hours on it when I installed it........before I put the engine in the boat, I installed a San Juan Engr full system I bought from http://www.oceaneastmarine.com/freshwater.html I still have it. It works fine.

Cheers,

Rick
 

thumpar

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With an engine run in fresh water it should be able to be converted later than one from salt. How many hours who know? Some of that will depend on the water in the lake, like what kind of minerals are in it and how clean it is. You may want to flush the block by pulling some core plugs to try to get any sand or junk out of the system before you convert.

How many hours are on your block?
 

Scott Danforth

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I converted my motor to FWC when it had 650 hours on it from the great lakes (primarily the bay of green bay, Lake Michigan, and a few outings on lake Winnebago).

At 625 hours, I had the motor on the stand, replacing heads, cam, oil pump, etc. as I switched to vortec heads.

the water passages were remarkably clean, however did have sediment in them from 24 years of use. with the motor on the stand, it was easy to clean the debris with an air gun and the motor upside down

Then I moved down here in 2012 with the boat, and I went to a heat exchanger prior to ever dipping the boat in salt water, I flushed the motor of any sand/sediment by using high-pressure water thru micro-bore tubing thru the drain plug holes. The HX was still clean when I pulled the motor at 850 hours to go to my big block.
 

tpenfield

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I converted mine engines with 740 hours (fresh water 100%) to closed cooling, but don't tell anybody, I'm going on the fourth season with them. So far so good. I will say that the thermostat housing and what I could see of the internal engine passages were in really good shape.
 

HT32BSX115

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I installed a San Juan Engr full system I bought from http://www.oceaneastmarine.com/freshwater.html I still have it. It works fine.
I guess I have to qualify the above statement. I have discovered a riser leak in the closed (port) side of the system. 10 years is pretty good though. I think one should maybe break the system apart every 5 years or so and replace those riser gaskets. OR, maybe put a 0-30 psi gage on the closed side of the system to detect loss of pressure (leaking gaskets) in the future.

After I get mine back together, I'm putting a gage on it. It'll be easy to look back there once in a while to see if the gage has pressure on it.

Cheers,

Rick
 

achris

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Up to 1996, most Alpha closed cooling kits were FULL systems and used only the existing Alpha drive water pump. They only recommended the Bravo style seawater pump if the water temperature was over 26C (79F).

I had that system on my 1994 4.3LX for 18 years. Worked with no problems at all. I replaced my exhaust elbows with genuine Merc stainless steel, while they were still available, and so had NO iron in contact with salt water. :D

Chris......
 
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tank1949

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Howdy,

I bought my 1997 Mercruiser 454/Bravo in 2006 to replace the 1987 460 King Kobra in my FourWinns 211 LIberator............... It had 122 NON-salt water hours on it when I installed it........before I put the engine in the boat, I installed a San Juan Engr full system I bought from http://www.oceaneastmarine.com/freshwater.html I still have it. It works fine.

Cheers,

Rick

THX!!!
 

HT32BSX115

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Can anyone tell me if the separate stainless block-off plates (sandwiched between gaskets) are better or worse than the Mercruiser block-off gaskets?
 

achris

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Used Merc 'block-off' gasket on my old engine (1994 4.3LX w/closed cooling) for 20 years. Never a problem. And as I also put SS elbows on, they were not removed in that 20 years.
 

HT32BSX115

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Used Merc 'block-off' gasket on my old engine (1994 4.3LX w/closed cooling) for 20 years. Never a problem. And as I also put SS elbows on, they were not removed in that 20 years.

That's pretty good service!

Are the stainless risers still available? Sure wish "dry-joints" were available for the 454.........
 

achris

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That's pretty good service!

Are the stainless risers still available? Sure wish "dry-joints" were available for the 454.........

Unfortunately not. They were pulled because of 'cracking'. Truth... They were pulled because once someone fitted them, they are forever (no buying elbows every 4-5 years. Did Merc out of a LOT of spare part revenue).....
 
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