toocoys
Guru
If twin 7.4L 454 engines are raw water cooled, can they be converted to a close cooled system?
Fresh water to salt?
- Thread starter toocoys
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Benthic2
Guru
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.
Delfin
Grand Vizier
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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.
OP
OP
toocoys
Guru
I’m looking at two. One is a 1979, the other a 1985, both are Chris Craft Corinthian 38’s. 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.
tiltrider1
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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.
Lepke
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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 180° 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.
tiltrider1
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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.
FF
Guru
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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
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
Last edited:
ranger58sb
Guru
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
OP
OP
toocoys
Guru
I’ve seen photos of the ‘84s 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 doesn’t have it.
I haven’t seen the ‘79 yet. We’re going to see it this afternoon.
ranger58sb
Guru
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
-Chris
