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Adding fresh water cooling to older engines ?

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Adding fresh water cooling to older engines ?

Old 01-14-2019, 06:58 PM
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Default Adding fresh water cooling to older engines ?

For years I have read read here that it is a bad idea to add fresh water cooling (closed cooling) to older engines. Rust clogging the heat exchangers, etc....
I am wondering if anyone has actually experienced or seen such problems or is it simply wives tails that get handed down.

My personal experience,.... in the early 1960’s my dad added Sen -Dure FWC to a 10 or 12 year old 155 hp Chris Craft flat head six and had no problems. About 1980 I added Sen-Dure FWC to about a 25 year old Graymarine 109 (flat head six) and had no problem. Two years ago I added Sen-Dure FWC to my pair of 60 year old Chrysler Crowns and they are doing fine.

What do you say? Personally experienced problems or rumors and maybe wives tails?
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Old 01-14-2019, 07:22 PM
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I did it on 2 small block Fords. I thought I cleaned the water passages pretty well when added the system, but when I freshened the engines a few years later, the blocks were full of rust and crap.

Newer GM blocks are thinwall castings, and are often not as hard as older cast iron.

tough call, but fresh water cooling is the best for both performance and engine longevity both internally and cooling system wise.
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Old 01-14-2019, 07:25 PM
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I don't know about flakes clogging things but adding FWC to an already exposed engine seems like the horse is already out of the barn. The two differences I recognize is that a FWC engine can be rebuilt and can run a 180° thermostat. Otherwise there is no real benefit.

With a classic engine that you want to preserve I would take the leap, but for a cast iron chevy block, I can buy a new long block for just a bit more than the FWC kit will cost.
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Old 01-14-2019, 08:07 PM
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I did it on a couple 350s that had close to 500 hours on them and a season in the salt and have never looked back. I would only do it for the saltwater issue though, no need to be concerned in freshwater is my opinion. Mrcool.com
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Old 01-14-2019, 08:56 PM
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I did T/5.0 mercs a few years ago. had about 300 hours on fresh, brackish and salt water, Installed full FWC. My use was 3 years of salt. flushed bock and manifolds for about a week before installing.
Was very aware of the opinions about doing this on an older engine, including rust and scale. so I was diligent in the flushing and cleaning of outlets.
Installed kits and boat ran fine until the end of the season when I came of a pretty big wave, within 15 minutes both engines overheated. The left side manifolds were full of scale and rust, I was under the impression that they had been replaced, I was wrong as only the risers were done.
Replaced manifolds, risers and water pumps, has run fine since - approximately 100 hours.
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Old 01-14-2019, 09:01 PM
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I should have added that my three experiences were all on total salt water engines, including my Crowns that lived inside Manasquan Inlet NJ for 45 years.

I agree there should be no issue,.. and not much reason for fresh water (lake) engines.
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Old 01-14-2019, 09:40 PM
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I should have mentioned,,, the boat we did was a 97 so the manifolds and risers were original. Once we tore into things to add the kit we quickly made the assessment that it was time to replace. That made the job easier and cleaner. We could not get the plugs out of the original manifolds. I went with Bar. From my limited research found them to be superior.
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