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Old 06-15-2018, 06:19 PM   #1
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Question Fresh water to salt?

If twin 7.4L 454 engines are raw water cooled, can they be converted to a close cooled system?
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Old 06-15-2018, 06:31 PM   #2
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You may want to provide a little background on what you are considering. With enough time and money, anything CAN be done....but does it make sense or not is a different issue, and depends on your circumstances.
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Old 06-15-2018, 06:47 PM   #3
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If twin 7.4L 454 engines are raw water cooled, can they be converted to a close cooled system?
I converted a salt water cooled Saab to coolant and it wasn't difficult. An appropriately sized exchanger and sea water pump, plumbing the raw water though the exchanger and to the water lift mufflers and I think you're there. Whether it's worth it is a separate question.
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Old 06-15-2018, 10:54 PM   #4
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You may want to provide a little background on what you are considering. With enough time and money, anything CAN be done....but does it make sense or not is a different issue, and depends on your circumstances.
Iím looking at two. One is a 1979, the other a 1985, both are Chris Craft Corinthian 38ís. Each have twin 454 engines and have been fresh water boats. Neither of the listings mention close cooled systems, and since we are in salt water I need to be sure.
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Old 06-16-2018, 01:35 AM   #5
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Yes you can convert a raw water cooled 454 to fresh water cooled. You will need a fresh water thermostat housing and a heat exchanger. These parts are available. Some will tell you that you can use the raw water thermostat housing, you can but your engine will run cold except at high rpms.
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Old 06-16-2018, 01:36 AM   #6
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There are many makers of replacement heat exchangers that can fit your engines. You also need an expansion tank, a raw water pump and probably a 180į thermostat. Original pump probably will work for coolant. You can find a plumbing diagram online. The rest is just mechanical, mounts for the new pump, heat exchanger, and some hoses. Not hard to do.
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Old 06-16-2018, 01:50 AM   #7
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Are these engines merc, crusader, Volvo, or Harden Marine? 454’s were marinized by many and they are all a little different.
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Old 06-16-2018, 05:37 AM   #8
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Search for a full conversion kit, boats in lakes don't need it , but if running in salt water a conversion is almost mandatory.

In past days a direct sea water cooled engine was expected to last 7 years , or so.

When gas engines lasted 1,000-1500 hours or so it worked OK
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Old 06-16-2018, 06:36 AM   #9
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Iím looking at two. One is a 1979, the other a 1985, both are Chris Craft Corinthian 38ís. Each have twin 454 engines and have been fresh water boats. Neither of the listings mention close cooled systems, and since we are in salt water I need to be sure.

Maybe confirm they're really raw water cooled first, before spending too much time researching? Might be they simply didn't list that factoid?

-Chris
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Old 06-16-2018, 07:11 AM   #10
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Maybe confirm they're really raw water cooled first, before spending too much time researching? Might be they simply didn't list that factoid?

-Chris
Iíve seen photos of the Ď84s engine but I know nothing of mercruisers. If the heat exchanger on the Merc looks anything like the exchanger on my 327F engines (big tank over the serpentine belt) then it doesnít have it.

I havenít seen the Ď79 yet. Weíre going to see it this afternoon.
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Old 06-17-2018, 06:45 AM   #11
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We're at an Antique and Classic Boat Show this weekend. LOTS of Chris Craft... several woodies, but one of the larger ones is a 1967 47' Commander... and it look brand new.

-Chris
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