Yanmar 3GMD: Rydlyme or other marine descaler in older engine

[mikedefieslife]

Originally Posted by Lepke

When I was a kid in the 1950s, most gas engines were raw water cooled. When rebuilding one, you could find some water passages almost completely blocked. They also rusted out. It was common to replace the head because of wastage. I never owner a raw water cooled diesel, but if I did, I'd convert it.

I use Rydlyme in my 70 year old Detroits without issues.

Why would you bother converting it when in its standard raw state it's still likely to last 30 years. Most CF users would probably be dead by the time it needed replacing.

[fritzdfk]

Just for the sake of discussion, this from another forum. Referring to the reason raw water cooled engines use lower temperature thermostats.


No, that's backward, and wrong on multiple levels. Saltwater solutions at the saturation point will precipitate salt out of solution when the solution is cooled, not heated.



In general, this is true of all solutions. If mom ever taught you how to make rock-candy strings, you'll remember how this works.


Moreover, typical seawater is about 3.5% salt by weight. The saturation point for NaCl in H2O is 26% by weight. Salt can only precipitate out when the solution is saturated. There is no body of water on earth where the salinity comes anywhere close to saturation, so in effect, "precipitation" of salt out of seawater is literally impossible.



The real reason that raw-water cooled systems may use a lower thermostat temp is to increase the safety margin between the thermostat temp and the boiling point of the coolant. Antifreeze boils somewhere above 260 (depending on concentration) and seawater boils at just a tiny fraction of a degree above 212. Inside an engine, "pocket" areas of intense heat (tops of cylinder walls) can raise the coolant temp well above the temp at which the thermostat opens. In these areas, the coolant could transition to vapor and deprive these areas of full cooling, so we need to keep raw-water coolant well below that.



If you want to see this with your own eyes, put a pot of water onto an electric stove burner and watch as the bubbles form just above the coils of the heating element. You'll see this long before the entire pot comes to a boil.


Compounding the problem for seawater cooled systems (vs. freshwater) is the fact that the thermal conductivity of water decreases with increasing salinity.
__________________

[Compass790]

Originally Posted by fritzdfk

Just for the sake of discussion, this from another forum. Referring to the reason raw water cooled engines use lower temperature thermostats.


No, that's backward, and wrong on multiple levels. Saltwater solutions at the saturation point will precipitate salt out of solution when the solution is cooled, not heated.



In general, this is true of all solutions. If mom ever taught you how to make rock-candy strings, you'll remember how this works.


Moreover, typical seawater is about 3.5% salt by weight. The saturation point for NaCl in H2O is 26% by weight. Salt can only precipitate out when the solution is saturated. There is no body of water on earth where the salinity comes anywhere close to saturation, so in effect, "precipitation" of salt out of seawater is literally impossible.



The real reason that raw-water cooled systems may use a lower thermostat temp is to increase the safety margin between the thermostat temp and the boiling point of the coolant. Antifreeze boils somewhere above 260 (depending on concentration) and seawater boils at just a tiny fraction of a degree above 212. Inside an engine, "pocket" areas of intense heat (tops of cylinder walls) can raise the coolant temp well above the temp at which the thermostat opens. In these areas, the coolant could transition to vapor and deprive these areas of full cooling, so we need to keep raw-water coolant well below that.



If you want to see this with your own eyes, put a pot of water onto an electric stove burner and watch as the bubbles form just above the coils of the heating element. You'll see this long before the entire pot comes to a boil.


Compounding the problem for seawater cooled systems (vs. freshwater) is the fact that the thermal conductivity of water decreases with increasing salinity.
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Thank you for correcting my improper terms & description of mechanism of how salts get deposited in cooling water passages. When I said salts I didnt mean Nacl. I should have used scale & precipitation is the wrong word too. I should have said deposition.
The result is the same tho, over 60C the scale buildup in a raw water cooled engine is much faster.
Wont post the wrong explanation again
The result is the same

[Wotname]

Originally Posted by fritzdfk

Just for the sake of discussion, this from another forum. Referring to the reason raw water cooled engines use lower temperature thermostats.


No, that's backward, and wrong on multiple levels. Saltwater solutions at the saturation point will precipitate salt out of solution when the solution is cooled, not heated.



In general, this is true of all solutions. If mom ever taught you how to make rock-candy strings, you'll remember how this works.


Moreover, typical seawater is about 3.5% salt by weight. The saturation point for NaCl in H2O is 26% by weight. Salt can only precipitate out when the solution is saturated. There is no body of water on earth where the salinity comes anywhere close to saturation, so in effect, "precipitation" of salt out of seawater is literally impossible.



The real reason that raw-water cooled systems may use a lower thermostat temp is to increase the safety margin between the thermostat temp and the boiling point of the coolant. Antifreeze boils somewhere above 260 (depending on concentration) and seawater boils at just a tiny fraction of a degree above 212. Inside an engine, "pocket" areas of intense heat (tops of cylinder walls) can raise the coolant temp well above the temp at which the thermostat opens. In these areas, the coolant could transition to vapor and deprive these areas of full cooling, so we need to keep raw-water coolant well below that.



If you want to see this with your own eyes, put a pot of water onto an electric stove burner and watch as the bubbles form just above the coils of the heating element. You'll see this long before the entire pot comes to a boil.


Compounding the problem for seawater cooled systems (vs. freshwater) is the fact that the thermal conductivity of water decreases with increasing salinity.
__________________

Hmm... common compounds that collect inside a raw water cooled engine are calcium and magnesium salts (carbonates or sulphates), which are less soluble hot than cold.

Additionally chemical reactions can occur between two soluble salts to form insoluble compounds which are deposited as sludge or scale. Such reactions occur faster when hotter.

Both are very good reasons to operate the engine colder rather than hotter.

[Compass790]

Originally Posted by Wotname

Hmm... common compounds that collect inside a raw water cooled engine are calcium and magnesium salts (carbonates or sulphates), which are less soluble hot than cold.

Additionally chemical reactions can occur between two soluble salts to form insoluble compounds which are deposited as sludge or scale. Such reactions occur faster when hotter.

Both are very good reasons to operate the engine colder rather than hotter.

Thanks for educating us further Wotname

[Wotname]

Another data point; I have recently read the calcium carbonate content in seawater is very near saturation levels so that means any increase in temperature would cause these salts to precipitate out. Greater increase = greater deposits.

[lecrappe]

Originally Posted by Secondshift

Had another look at your photos. Photo 1 is on of your zinc anode mount. If the white powder is from a small saltwater leak the zinc housing can be resealed or replaced.
Unlikely to be a crack there.

The paint around the zinc mount bolt appears unbroken. Was this before you changed the zincs?


Regards

Wow, I wasn't getting notifications on my post and didn't realise there was so many replies! Thank you all! Anyway to answer your very observant question, yes this was before I replaced the zincs.

Thanks for your insight!

[Compass790]

Originally Posted by lecrappe

Wow, I wasn't getting notifications on my post and didn't realise there was so many replies! Thank you all! Anyway to answer your very observant question, yes this was before I replaced the zincs.

Thanks for your insight!

You should get email notifications when people post on yr thread lecrappe. Please let us know what happens temp wise after you descale & inspect.
Thanks to Wotname too for further education re the mechanism of the buildup