How to clean coolant side of a boat heat exchanger?

[sdowney717]

Took off to silver solder the drain port - zinc pencil holder
Noticed the inside is coated with brown red stuff that easily scrape off

This is a Sen-Dure unit. I can using my fingernail scrape off a layer of slightly sticky stuff from the tubes. This is the coolant side of the unit, not the raw water side.

Looking down the coolant side exit there is this buildup on the tubes, which I scraped off with a fingernail.

Whole thing. I removed it to silver solder the drain plug pencil zinc holder. I then JB welded the ends, and will repaint it. I notice when feeling inside at the cap, it also has a coating of the same stuff, so I think it is all over the inside of it. I may use spray on oven cleaner (lye) to clean it. I know this is made with copper-nickel tubing. All the rest is copper.

 

[97prizm]

I'd use the prestone radiator cleaner solution as a start then flush with hot water

 

[sdowney717]

I'd use the prestone radiator cleaner solution as a start then flush with hot water

of course might work.
Would that work without a running engine, like pour in and sit.
Boat is out of water, it is 37 footer.
Won't be running for a few months.
So no chance of a flush that has to work with hot coolant and running engine right now.

I may try spraying oven cleaner. I want to use something on it with it off engine.

 

[sdowney717]

https://flushingservices.com/blog/Boat-Heat-Exchanger

Found this, which claims don't use acid cleaners. Don't take to a radiator shop.
Claim is acid will ruin it.
I was not planning on anything except a DIY job
It is copper nickel tubing and copper shell is thick. It is much thicker than a car radiator.

 

[wings&wheels]

That advert from the flushing service smells a bit of fear mongering, but I would really recommend against oven cleaner as that stuff is strong. If it were me, I would use the radiator flush w/ very hot water on the bench, letting it sit and also agitating it, followed by a very thorough flushing. Also, the right radiator shop, one that does work on vintage vehicles, will surely know how to clean something like this properly. That being said, my antique inboard is raw water cooled so I am just slightly educated guessing

Old boat pics are always appreciated and you are in a nice part of the country for a boat! Been on the James a bit, always fun.

 

[RedSpider]

I used a gallon of muriatic acid (gasp!) and a couple gallons of water in a five gallon bucket. Because just like Maverick, I'm dangerous....

Remove the end caps and drain plugs......Dip one end in, wait a few minutes, dip the other end in, wait a few minutes, then use a hose to flush the crap out of it. This was a four inch exchanger off a Mercruiser 470... Big, thick, and heavy. Copper, I think? Dont remember, I sold the boat a few years ago. Never leaked and I did this every couple of years. Made a big difference in operating temps. Before the initial cleaning, it was pushing 195F+ even after just short runs at high RPM. After cleaning, it would run all day with the hammer down and barely crack 170F.

Obvious safety cautions apply. Old clothes, eye and hand protection, dont breathe the fumes, a big box of baking soda and a running hose by your side, etc etc.

Anyway, dont do this. You'll die and your boat will blow up. I'm not recommending anyone else clean their's this way, I'm just saying what I did. Nothing else seemed to work very well.

 

[Cujet]

Citric acid in a hot solution will work pretty well.

 

[sdowney717]

Guys, I am trying white vinegar. Got couple gallons. I used rubber hoses to close off the openings.

After an hour it is slowly dissolving. I put my finger inside the fill, scraped at it and it is loosening up, turning into a red brown dirt.
It may be engine block rust mixed with something sticky.

I wonder if you could do this another way, like flush out the antifreeze. Then refill system with vinegar and run it up to temp and let it soak a while.
That would clean the whole engine.

 

[sdowney717]

And found another product which has good reviews
https://www.amazon.com/gp/product/B00JJ1FB28/ref=ox_sc_act_title_1?smid=ACCN4F2I5XM2M&psc=1

Nothing worked for this guy till he used that stuff.
And I think you can simply use it as a soak.

 

[thastinger]

Dawn dish soap...the max/extra version of it. Put a couple squirts in there straight, add hot water and slosh it around for a bit and let it sit for a few. See if you like the results, rinse and repeat as necessary.

 

[Donald]

Some pump through "Barnacle Buster" through the raw water side.

I think it may depend if the boat was run in salt or fresh water.

 

[sdowney717]

Yeah, raw water side gets calcium scale buildup, which acid eats.

I dumped out the vinegar, and put in gasoline, E10, which is definitely fully dissolving this stuff.
I scraped some of the crud and put it in some gas and it sort of looks like stop leak.

in a day, I will dump the gas and flush with water and see how clean it is.
Very happy to see how soft the coating has become.

The dumped vinegar did get a little dirty

My setup
Full of a gallon of gasoline

The scraped crud dissolved in gasoline

 

[Kira]

As suggested in post #7:
See what citric acid (common cooking ingredient) can do.

There's a chance gasoline didn't touch it and all you got were some 'free bits' and staining.

My sister had a heater core which had a variety of radiator leak-stop products clogging it.
I know this is not your situation.
Dish cleaner, floor cleaner and Lysol didn't touch it.
However, gasoline worked on that stuff.
I think you have different dirt and citric acid (buy a 10 lb. bag through Amazon) is benign enough a product to try.
Use a cup in a quart of hot water.

Also, can you get some sand and swish it around WITH the citric acid?
This is how servicemen cleaned their canteens.