Coverting from RAW to FRESH water cooling

"Guys: 1987 4.3L (1996 lo

"Guys: 1987 4.3L (1996 long block) I/O

I have read some discussion about this issue, but would like to convert so I can fish longer w/o winterizing after each trip. The residual rust and scale that is now in the engine is probably my main concern.

If I convert to Full FWC, can I run water and chemicals thru the block to clean it and flush out the crap before adding antifreeze?

Will I need to add manifold risers or just change the gaskets to route the antifreeze?

Please be frank with your comments!

Guy"

"Converting to Freshwater Cool

"Converting to Freshwater Cooling will Not accomplish the objective your looking for.....

There'll Still be a Heat-exchanger Full of Raw Water,....
You'll Still have to Drain the motor,.... Just at Different Places......

And,..... No,...
Without a Total Tear-down,....You'll Never get a Used motor Clean enough......

I continue Fishing til I can't get the boat off the trailer at the launch, because of the Solid Ice....
When coming back in from a trip,....
It might take 5 minutes to pull my drains,+ be ready for the following weekend......"

"Coverted my 5.7L to fresh wat

"Coverted my 5.7L to fresh water colling a few years ago. It had a few salt water hours (100 or so) on it before the conversion.
- When the engine is not running, the raw water side of the Hx drains back through the outdrive. If the boat is out of the water, it's bone dry. While I was keeping it in the water, it drained to the water line, which is below the Hx. (Not assuming yours will do the same, but it works out kinda nice for me!)
- When I first converted, after running it for a couple of days, I drained and flushed the freshwater side. The water went form nice green anti-freeze to near black. It took about 3 good flushes to get it cleaned up, but it's been staying pretty clean ever since.
- The fresh water conversion kit will give you an option to either circulate the fresh water through the manifolds and spacer blocks (Full FWC) or leave them raw water cooled (Partial FWC). If they are more then a couple years old, I would replace them and go with the full FWC option.
- The exhaust elbows (risers) will stay raw water cooled regardless... 4-5 years in salt water is about all you'll get out them.
- Change the T-stat to a hotter one... 180F. This will also necessitate changing the water temperature alarm sending unit to a higher setpoint commensurate to a fresh water cooled engine.
- Draining the raw water side of Hx, if yours doesn't drain on its own, would typically require either pulling a hose off, or if it's situated properly, pulling the zinc plug out.
- The rust and scale that's in there now is in there regardless. Some will come out as discussed above. The bottom line is once you do the conversion, that process of converting iron into iron oxide will stop... engine block will last longer. That still leave the question of whether the conversion is cost effective... so what if the engine block lasts longer, will everything else last as long? Or, will you gain the added value by not having to dick around with flushing and draining everytime you use the boat?"

"Troy: Thanks for your input.

"Troy: Thanks for your input. My 96 reman. 4.3L only has gauges and a set of matching idiot lights. Why should I change T'stats from the recommended 140 deg. to 180 deg.? Also, the SB exhaust man. is 2 yrs old while the port side is orig. and was welded once. The risers were pulled last summer for inspection and cleaning--both are good. Don't have spacers on them. Do I need them for complete FWC? This engine only has about 200 hrs. on it and for about $650 it can be complete FWC.

Thanks, Guy"

"Guy,
Regarding the T-stats:

"Guy,
Regarding the T-stats: Raw water cooled engines aren't a closed circuit, therefore don't operate under any system head (pressure), just the relatively low differential pressure established from the two pumps to establish flow. Therfore, raw water cooled engines are set to run cooler to prevent localized boiling (next to the cylinder walls). Some localized boiling is actually better for heat transfer, but too much could result in steam blanketing in the water jacket (unlike water, steam has almost no heat capacity, therfore won't tranfer heat away from the cylinder wall). Also, in salt water, the resulting salt and mineral deposits from the water boiling off results in a very detrimental effect... when those deposits are rewetted, you've now set the stage for severe and rapid pitting type corossion.
A closed circuit (FWC) system operates under pressure, about 7 or 8 pounds usually. This correlates to a saturation temperature (where boiling takes place) of about 240°F or so. So, with that added pressure to surpress boiling, the engine is allowed to run at the preffered (more efficient) higher temperature of about 180-190F.
Regrading the manifolds, the welded one kinda scares me. If it were mine I'd replace at least that one.
The risers sound OK.
The spacers are not a necessity and no you don't want to put those in if they're not already there. All they do is make the risers line up to the 'y' pipe in varying space and clearance applications depending on the boat.
What you'll get with the kit are gaskets that go in between the manifolds and risers that have the coolant channels blocked off. The fresh water will go from the Hx, into the tops of the manifolds and out the bottom, then back to the engine. If you had spacers, the blocked off gaskets would go above the spacers and the coolant would flow into the spacers, then into the manifolds, then out the bottom and back to the engine.
The raw water leaving the Hx will flow into the risers and out with the exhaust. The gaskets mentioned above seprate the raw and fresh water flow paths.
These guys are a little more expensive than what you've found, but they do have a downloadable .pdf file so you can see what you're getting yourself into.
http://i-netmarine.com/fwc/fresh.htm"

"Thanks to everyone that repli

"Thanks to everyone that replied to my post. I'll consider all the comments and ideas and determine which way I'll proceed.

For reference; I have been using the following supplier: www.ebasicpower.com
Their prices for marine maintenance parts are very reasonable with fast service and free shipping w/min. purchase. Guy"