Cleaning raw water cooling

[mrybas]

Hi,
I was changing impellers and found broken off fins, so removed the heat exchanger cap to find the broken impeller fins. The end of the heat exchanger looked pretty nasty, so I scrubbed the end with a green scrubby pad, then used a wooden BBQ skewer to poke down the tubes.
It looks much better now. Is there any use in sucking up some h2o/vinegar mix and letting it sit for a few hours?

[Pyxis156]

Not an answer to your vinegar question, but that is a lot of fairly large debris in the heat exchanger! Do you have a raw water strainer upstream of your engine? I would imagine the impeller having to process some of those debris would contribute to its demise.

Regarding soaking it, Practical Sailor recently reviewed products for this application and I seem to recall that vinegar was their "slow but safe" option. I can't remember what they ultimately recommended but can look if you are interested.

[mrybas]

Originally Posted by Pyxis156

Not an answer to your vinegar question, but that is a lot of fairly large debris in the heat exchanger! Do you have a raw water strainer upstream of your engine? I would imagine the impeller having to process some of those debris would contribute to its demise.

Regarding soaking it, Practical Sailor recently reviewed products for this application and I seem to recall that vinegar was their "slow but safe" option. I can't remember what they ultimately recommended but can look if you are interested.

Yes, there is a raw water strainer. I don't remember the mesh looking unusually large, but I'll check tomorrow.
Can you look at the PS article when you get a chance?

[Frankly]

I use a brass pistol cleaning brush (32 cal on Yanmar 3GM, cut off rifle extension, and a battery powered drill. Kept two GM series cool for over twenty years just doing this every few years.

There is usually a little crap and an occasional impeller piece from time to time. I have Perko strainers and keep them clean. Crap just happens.

In case the light bulb hasn't gone off yet, that looks like a 3 pass exchanger. Take a look at your cap and gasket.

[Pyxis156]

The Practical Sailor article tested eight descaling chemicals. CLR was their "Best Choice" for cleaning engine cooling systems containing aluminum. Their overall winner was a product named Sew Clean.

Their bottom line was that "The only really serious mistakes are muriatic acid on aluminum, leaving any solution in the plumbing or cooling passages longer than recommended, or using a higher concentration than recommended."

Hope this helps...

[a64pilot]

Use the bore brush.
I went to clean my heat ex on my 4JHE and put it in a mix of muratic acid and water, this was how I figured out the thing apparently contains a large amount of zinc.
Any acid, even vinegar will react with zinc

[mrybas]

Originally Posted by a64pilot

Use the bore brush.
I went to clean my heat ex on my 4JHE and put it in a mix of muratic acid and water, this was how I figured out the thing apparently contains a large amount of zinc.
Any acid, even vinegar will react with zinc

My last boat had a yanmar 4jh and it didn't have engine zincs.
This engine is a Nani N3.21 and does use engine zincs.

[Lepke]

I use Rydlyme because it does a good job and is biodegradable and legal to dump in most sewer systems. A gallon is advertised to dissolve 2 pounds of calcium carbonate scale. I have 3 zincs per engine and usually remove them. If left in, zincs get small pits.

[a64pilot]

Originally Posted by mrybas

My last boat had a yanmar 4jh and it didn't have engine zincs.
This engine is a Nani N3.21 and does use engine zincs.

I think, it's just a guess really, that it doesn't have zincs, because the heat exchanger has so much of it, likely years worth I'd assume?

[mrybas]

Originally Posted by a64pilot

I think, it's just a guess really, that it doesn't have zincs, because the heat exchanger has so much of it, likely years worth I'd assume?

Not sure what you mean.
I had a yanmar 4jh5e that did not have replaceable engine zincs in the last boat.
My current Nani 3.21's have pencil zincs in the exhaust elbow.

[wsmurdoch]

Originally Posted by Frankly

I use a brass pistol cleaning brush (32 cal on Yanmar 3GM, cut off rifle extension, and a battery powered drill. Kept two GM series cool for over twenty years just doing this every few years.

I do the same with a Yanmar 3HM35F, but I have never needed a drill. I guess my junk is softer. Next time I do it, I'll think about a drill. The kit is less than $10 at WalMart (my favorite marine store).

[Dsanduril]

Originally Posted by mrybas

Not sure what you mean.
I had a yanmar 4jh5e that did not have replaceable engine zincs in the last boat.
My current Nani 3.21's have pencil zincs in the exhaust elbow.

I think he is referring to dezincification of the brass/bronze body of the HE itself. Most brass/bronze alloys contain some amount of zinc. In dezincification the zinc is selectively removed (by corrosive/galvanic action), leaving behind holes in the alloy and a very porous, weak matrix of copper.

Dezincification is particularly a problem in alloys with high zinc content (>15%), with fluids that are not neutral pH (both acid and alkaline solutions can lead to zinc removal), and fluids with high chloride content (salt water). A proper marine HE should use dezincification resistant alloys, but one borrowed from a mass produced product may not.

That said, an occasional acid wash followed by good rinsing will not lead to excessive zinc removal, but leaving enough acid/cleaner in the system due to poor rinsing can lead to long term dezincification.

[a64pilot]

Originally Posted by Dsanduril

I think he is referring to dezincification of the brass/bronze body of the HE itself. Most brass/bronze alloys contain some amount of zinc. In dezincification the zinc is selectively removed (by corrosive/galvanic action), leaving behind holes in the alloy and a very porous, weak matrix of copper.

Dezincification is particularly a problem in alloys with high zinc content (>15%), with fluids that are not neutral pH (both acid and alkaline solutions can lead to zinc removal), and fluids with high chloride content (salt water). A proper marine HE should use dezincification resistant alloys, but one borrowed from a mass produced product may not.

That said, an occasional acid wash followed by good rinsing will not lead to excessive zinc removal, but leaving enough acid/cleaner in the system due to poor rinsing can lead to long term dezincification.

No, I'm pretty sure my entire heat exchanger insides, the removable part, tubes and all is heavily zinc coated.
It sure looked and acted that way when put into a mix of muratic acid and water anyway.

I have wondered why Yanmar would be so foolish to leave out a zinc for the raw water side of the cooling. I surmise maybe they didn't.
I know they are needed and useful, code the disappear on boats so equipped and if they weren't needed, they wouldn't.

[wsmurdoch]

Originally Posted by a64pilot

I have wondered why Yanmar would be so foolish to leave out a zinc for the raw water side of the cooling. I surmise maybe they didn't.

My Yanmar 3HM35F has no zincs on either the raw water or the circulating coolant. It is a 1988 model with around 9600 hr.

[lancelot9898]

I have a Perkins 4-108 and over the years(30 years) have cleaned that heat exchanger probably 3 times. I've had success with a diluted solution of muratic acid and letting it soak for a minute or two. Then putting the HX into a solution of baking soda to neutralize the acid. Used a gun cleaning rod to pass through the tubes and getting them all to shine. As long as the engine is cooling properly, I leave it alone.