Engine Flushing for Salt Water

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.

Roger Long

Senior Member
Joined
Jul 14, 2015
Messages
451
Location
Albany
Vessel Name
Gypsy Star
Vessel Make
Gulf Star 43
Strange, I can't get an answer through Google on this. Help.

All questions and answers about cooling system flushing seem to be aimed at descaling for maximum cooling efficiency. Our engines run at about 25% horsepower in our normal cruise. The heat exchanger I just took off had about half its RW tubes plugged an I never saw any temp rise even when running WOT to blow out the exhaust.

Our port engine ran for about a week with salt water instead of anti-freeze for coolant. I've filled and drained it a half dozen times with fresh water. My only concern at this point is getting rid of any salt left in it.

What, if anything, should I flush it with before re-filling with anti-freeze? We'll have a brand new heat exchanger so no worry about de-scaling that.
 
I have not had any experience with a situation such as yours, but I ran Salt Away through my dinghy outboard while doing the saltwater section of the Loop and my friends do the same with the outboards on their boats in Florida. It's a salt neutralizer and sounds like it should work for what you are trying to do.
http://www.saltawayproducts.com/
 
This might help if the equivalent product is available over there. www.saltoff.com.au - Marine Products
There are boat engines which use raw water as coolant, which is what you did. I once looked at a boat with twin 80s Lehmans so cooled, lots of shell came out the exhaust when it was started. It`s not the end of the world, but getting rid of the salt residue would be a good idea.
 
I use Vinegar to flush out my engines. Works pretty good.
 
I had a boat raw water cooled engines, twins. I had it converted to fresh, coolant, cooling.
Never had a problem with it. No cooling or rust issues after three years at which time we traded for our current boat.
I suspect if you have clean fresh water flushed several times then it will be just fine. When you do the fresh flushes you should run the engine for a bit circulate the water.
What little salt residue remains won't be enough to worry about.
If you are still concerned then instead of a two year change interval make it a one year change interval. Then go back to your normal changeout interval.
 
I used Barnacle Buster in our engines last year. Saw a drop of 5 degrees on one engine and 10 degrees on the other. I just let the raw water pump draw it in and let it sit for 7 hours then started engines to flush it out. This only treated the raw water side though. Did the same to genset and A/C units.
 
If you are just flushing the fresh water (coolant side) of an engine, I would just use something like Prestone radiator flush. The heavy duty recommendation is leave it in the engine for a couple days of light usuage, then fresh water flush and refill with coolant.

Takes out rust too.
 
If you are just flushing the fresh water (coolant side) of an engine,

But, the fresh water side also became the salt water side :)

I'm thinking this is the option I'll go with. Is it really possible that tube failures are so rare that there isn't a common wisdom answer to this.

BTW, it looks like it is just one tube leaking. I think I can clean it up and solder or epoxy that tube shut and keep the old unit for a spare.
 
FWIW, Cummins recommends Restore for flushing the fresh water side. I've used Rydlyme and Barnacle Buster for flushing raw water passages, including those for the ACs.

FWIW, I also used Barnacle Buster (similar to Sew-Clean) to unclog the toilet discharge hose after inadvertently letting the uric scale dry out...

-Chris
 
But, the fresh water side also became the salt water side :)

I'm thinking this is the option I'll go with. Is it really possible that tube failures are so rare that there isn't a common wisdom answer to this.

BTW, it looks like it is just one tube leaking. I think I can clean it up and solder or epoxy that tube shut and keep the old unit for a spare.

I know, but now you have 2 systems. Coolant and raw water. Once the coolant system is closed, use the Prestone Heavy duty cleaner...I have heard the active ingredient is Oxylic Acid which is good for calcium and rust, probably salt crystals too. Its as good as anything that has been mentioned so far as an engine block cleaner. Can remember who mentioned dishwashing detergent for that application, but I wouldnt do snything that isnt recirc pump safe unless an engine guy said OK.

Then banacle buster for the raw water side but you said the HE is new, so unless the rest of that side iscsuspect, then no need.
 
Last edited:
I would also stick to the Prestone product or similar for the coolant circuit.
 
Too be clear, Roger is asking if he should flush his COOLANT side after it was contaminated with salt water due to an exchanger leak.

I am a retired chemical engineer who worked in the chemical cleaning industry early in my career, so:

When you ran your engine with significant salt water in the coolant system you were probably running it at 180+ degrees, the typical coolant system temperature. This is high enough to precipitate calcium and magnesium salts out of the sea water mixture even if run for a short number of hours. But it is not like your raw water system that can build up visible deposits over a number of years. This only occurred for a short while and there was a finite quantity of salt water in the coolant.

You need a mild acid to dissolve those salts. Barnacle Buster is good for the raw water side, but i wouldn't use it for the coolant side. The milder Prestone or similar product with oxalic acid should be sufficient to dissolve any deposits. Use it as the supplier recommends which is probably to fill and run the engine for an hour or so to heat and circulate. Then drain and flush a couple of times and refill with 50/50 antifreeze.

David
 
Back
Top Bottom