Why Salt-water Cooling?

Xsbank said:

You can't run salt water in a diesel. You must use coolant (in good condition). The cylinder walls expand when the piston sweeps the cylinder and contract once it has gone by. If the coolant is old or salt water, there is cavitation against the cylinder, causing overheating. Scored cylinders, broken rings etc.

Anybody ever shot the temperature of the salt water as it leaves the coolant daisy train and is injected into the exhaust?

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Huh,??
You can run salt water in a diesel. Many thousands of diesel engines have been designed and built to be cooled by salt water; mainly from the 1960's - 1980's.

I am no longer aware of any diesel manufacturer that still produces these, mainly due to economic (heavy walled blocks cost more) and enviromental reasons. (salt water cooled diesels must be run at lower temperatures to minimise salt buildup in the water jacket; lower temp = higher emissions)

Xsbank said:

You can't run salt water in a diesel. You must use coolant (in good condition). The cylinder walls expand when the piston sweeps the cylinder and contract once it has gone by. If the coolant is old or salt water, there is cavitation against the cylinder, causing overheating. Scored cylinders, broken rings etc.

Anybody ever shot the temperature of the salt water as it leaves the coolant daisy train and is injected into the exhaust?

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I had a generator powered by a raw water (salt water) cooled Lister-Petter diesel. The salt water corroded a hole in the aluminum head, but it ran fine, the cylinder bore was fine when I threw it away.

I have taken water temps at the exhaust elbow on a couple of engines, I think they were all in the 90 to 110F range if I remember correctly.
That's with sea water in the mid 60s F.

The Cummins B series could easily be raw water cooled as it is a parent bore block, no liners. A wet liner engine would not be suitable at all. A dry liner engine would be debatable. B series would benifit from a SS water pump impeller, the engine pump, not the rubber impellor pump. A dry riser elbow on the exhaust with water injection below the exhaust port would be ideal. Passive block/exhaust manifold drains incoorperated into the system would help. Add a freshwater flush system for use befor shutdown. I have never heard of cylinder walls "expanding" causing overheating. Any proof ? as I would very interested to know.

I think you could raw water cool a B Cummins without much trouble. A few things were different on chevy gassers: Change core plugs to brass, stainless circ pump impeller, different thermostat housing to do a "feed and bleed" flow, while maintaining circulation. Also a thin SS head gasket and not a steel/composite. Also a normal B has a bypass flow loop through turbo and exhaust manifold, and the ports are too small to accomodate all the flow you would want from the engine.

More I think about it, it gets more complicated to do right. The chevy raw water cooled engines were actually engineered pretty carefully with some very unique parts.

Xsbank said:

No Mast, exactly!

There's another thread here where a Cummins engine transmission cooler failed and there is a milkshake in the trans. Why use salt water with its accelerated corrosion rate for oil coolers? I don't have my Cummins manual here but I'll bet if the salt water that goes through the coolers has already been through the heat exchanger and the after cooler I'll bet it's close to coolant temperature anyway?

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It depends on the operating temp range for the transmission and the normal operating temp of the engine coolant.

Operating temp range on my transmission is 104 - 176 degrees. Engine coolant temps run pretty much at the maximum for the gear oil. Coolant would be unsuitable for cooling the gear oil in my application.

My foggy memory of the 50s says that the only pleasure boats that had FWC were 50 footers or thereabouts. Most engines were flathead gasoline and SWC.

In my 1953 Motor Boating magazine there is a full page ad for Crysler's "Crown" engine. It may be the straight eight because they talk about it's smoothness in the very extensive text .. but no mention of FWC.

Ok, you can't run salt water in a 'modern' diesel.

If your coolant temperature is in the same range as the trans operating temperature, what is the problem? If the manufacturer says run it at a certain temp, why do you think less is better?

I'll say it again, I don't have salt water in my boat, it is keel cooled. I also don't have a heat exchanger, the transmission and oil are cooled by the engine coolant. I think you are all at risk of a salt-water induced cooler failure that can destroy your engine or your transmission and I'm wondering why you are happy to let this condition continue?

This boating stuff is like religion, so many of you cling to your beliefs as if a different way of thinking will rock your world. It's just boating...

Somebody asked for "The Proof." Here is some, it's not hard to find this stuff.

"Diesel engines often suffer from cavitation caused by the extreme pressures encountered in the combustion cycle. The diesel combustion cycle creates distortion. On the intake stroke, air is introduced into the cylinder. The intake valve closes and the piston starts traveling up the bore, compressing the air that was just ingested. Right before the piston reaches TDC (top dead center), diesel fuel is injected into the cylinder. Then a massive explosion happens and starts forcing the piston down in the bore. This massive explosion causes what is called a “jarring effect,” which can’t be seen by the human eye, but does actually happen. Tiny air bubbles can attack a cylinder liner with a force as much as 60,000 psi. This “jarring effect” is found mostly in wet liner engines, those diesel engines that have replaceable cylinder liners. When the explosion occurs, the liner distorts and rocks inside the block, actually moves away from the engine block, ingesting a small amount of air into the cooling system. This small amount of air makes tiny bubbles that form around the cylinder’s liner and these tiny bubbles can then attack the cylinder liner with a force sometimes as much as 60,000 psi. This actually pings the liner and starts shearing away the liner microscopically. After a period of time, this shearing will cause small pin holes to appear in the liner, which eventually make their way through to the cylinder bore. When this happens, coolant will start to enter the cylinder bore and eventually the oil pan. The customer will complain of losing coolant while the oil level is rising. While it may sound hard to believe, this problem has been around for years. Luckily, there is a solution — supplemental coolant additives or SCAs. The SCA will not stop the formation of bubbles, but will provide a protective barrier between the liner and the cavitation-causing bubbles. SCAs generally form a barrier with the use of nitrite, the level of which needs to be monitored in the cooling system on a regular basis. As the cavitation bubbles ping against the liner, they remove the layer of nitrite rather than the liner itself. The layer of nitrite is then replenished by the SCA. So it is a regenerative cycle, but can be depleted quickly. - See more at: http://www.knowyourparts.com/technical-articles/diesel-engine-coolant-maintenance/#sthash.H7vttA7z.dpuf"

For the record, it's not an "explosion." It's combustion. Big difference.

Don't cummins Bs use anti cavitation SCA in the coolant??

Neither gas nor diesels really like to run at lower temps. I think diesels would tend towards smoking and soot build up at 140F.


All this being said I had a low powered ferryman diesel in a sail boat that was raw water cooled in cold pacific sea water before I "knew of" all this important stuff. It ran fine for many years and probably still is.

Xsbank said:

I think you are all at risk of a salt-water induced cooler failure that can destroy your engine or your transmission and I'm wondering why you are happy to let this condition continue?

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I suspect it's because most boaters are not prone to jumping on the bandwagon of solutions that are looking for problems.

Sure, a failed heat exchanger can cause big problems in an engine or a transmission. Out-of-spec fuel can ice up and put a 777 on the lawn at Heathrow because the engines won't spool up on short final. A computer can go nuts and cause a Washington State ferry to take out a ferry terminal.

All of these things have happened and continue to be possibilities. But the fact is, they are very rare occurances. The raw water heat exhanger cooling system concept used on most recreational power boats has been around for decades and is used in millions of boats around the world. If this was a failure prone concept, it would not have this huge legacy of reliability.

Like every other system subject to wear or degradation over time, it requires oversight and action before failure occurs.

The raw water cooled exchanger system has has its advantages. If it didn't, it wouldn't be the most prevalent cooling system used on boats of this type worldwide. Keel-cooling has advantages too, as does dry-stack. And all three systems have disadvantages.

So to answer your question, and speaking only for me, a heat exchanger failure is not something I even spend time thinking about because we regularly examine them, and in the case of the small ones, we change them out when they start showing signs of degradation. We also reduce the risk of failure by using the more expensive but longer lasting cupro-nickel exchangers.

And, when we have changed them because they had developed a pinhole leak at the drain plug in one case, or were simply showing signs of age in other cases, the inside of the coolers we took off were always immaculate.

So, if an operator is conscientious about the condition of the heat exchangers (and hoses and the rest of the powerplant/drivetrain system) I view it as a non-problem.

Same as when I get on a 777 I don't worry about out-of-spec fuel that's going to freeze up and gel and muck up the fuel system and cause the engines to go non-responsive. It can happen--- I know that--- but the chances are staggeringly high that it won't.

Xsbank;
Good interesting read in your "proof" post. The stress during the combustion cycle in any engine is massive; more than most people imagine. I for one, wasn't aware of the cavitation issue; only simple salt water corrosion. Perhaps cavitation was the demise of my old volvo. I didn't bother doing an autopsy.

As an off topic side note - I used to work for a power generation company which ran engines (mainly Caterpillar 3516's) fuelled by a variety of sources; landfill gas, coal seam gas etc. We found that the engines run from a fuel containing a high levels of inert gas such as CO2 ran for an incredible number of hours (up to 80,000 hours) at full load before needing major rebuilds.
This was due to the CO2 slowing down the combustion process, resulting in much lower peak cylinder pressures and less stress on rings, liners, bearings, & crankshafts. They still obtained the same power output.
So yes - the shock from combustion certainly does due some damage.

Maybe at 120 hp and non turbo the B series would be a candidate. I dont know, never having done it. And apparently no one else has either. As for the smaller passages and diminished water flow, it doesnt take as much "raw" water to cool an engines flow wise as it does coolant due to the fact that there is no heat exchanger. Brass freeze plugs are not a problem or the SS waterpump impellor. Copper sheet head gasket would be easy. Looks like all the negatives could be addressed. Even the "air bubble" theory (only a problem on wet liner types) because any air would be pushed out by new water constantly.

What is the "air bubble" theory?

Xsbank said:

You would have far less maintenance, the oils would never get hotter than the coolant.

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Xsbanks, as I see it, if the tranny oil is to be cooled by the engine coolant it would have to be hotter than the coolant. How much hotter I don't know but if it is 10º to 20º hotter then the tranny oil would be at around 200º which as posted above is too high.

(A transmission is probably only 90% to 95% efficient. With a 120 hp motor at say, half power, the tranny needs to dissipate almost 5 Kw. As such a 10º to 20º or more temperature difference in the heat exchanger would not seem unreasonable.)

Gear coolers in the engine coolant circuit are usually placed somewhere near the discharge of the coolant heat exchanger, so the coolant temp is a good bit lower than the normal say 180F coming out of the engine.

Xsbank said:

What is the "air bubble" theory?

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I think he's talking about cavitation corrosion and why you should run astm d6210 coolant in wet liner engines. Avoiding silicate additives as well should you have a keel kooler.

Here's some stuff from Bob Senter on the subject.

Diesel Marinization - there's more to it than you'd think!

Let's clear up what "marinization" means. You start out with an Assembled block, cylinder head and fuel system, then
add the peripherals that make it a marine engine. This process often makes or breaks an otherwise perfectly good
diesel. There is a lot more to it than first meets the eye.

1. A larger, preferably heavily cast, oil pan is specified for maximum oil capacity, but it has to be shaped so that it doesn't
make the engine so tall it will be uncompetitive with other engines and difficult to install. It also needs provisions for
different dipstick locations and oil drains compatible with low bilge locations and tight stringers.

2. A different valve cover may be specified for additional oil vapor/mist separation, noise dampening and resistance to
rust and corrosion. Marine engines often require optional oil fill locations and crankcase breather choices.

3. A marine-specific exhaust manifold must be installed - something completely different from any other application. The
Coast Guard requires the manifold to be heat shielded so that if something flammable comes in contact with it, there's
no fire. This can be accomplished with very expensive insulation (space shuttle tile material) and heat shields. That
improves engine efficiency about 10%
compared to a water jacketed manifold because more heat is available to run the turbocharger. Turbochargers and
exhaust elbows must also be insulated or water jacketed. Again, water jacketing reduces efficiency but may present a
slightly cooler surface for decreased radiated heat to the engine room. Higher output engines absolutely REQUIRE
water jacketed exhaust system parts to absorb the thermal stresses - dry insulated manifolds crack under those
conditions. Needless to say, water jacketed parts in expensive diesels are cooled by the engine's antifreeze/coolant
mixture because sea water is too corrosive.

4. A marine specific intake manifold is generally required for packaging efficiency with the cooling and exhaust systems
that are completely different from land bound applications. In order to meet current NOX emission requirements,
turbochargers are almost universally required on any engine over 100 HP. Turbocharging raises the temperature of the
air going into the intake manifold, requiring some sort of cooler to keep it cool enough to allow the engine to meet Nox
emission laws. <<Nox is formed by high combustion chamber temps.>> That "aftercooler" component may be either
seawater cooled or jacket water cooled. If it is seawater cooled, there is a strong possibility that the engine will be
destroyed by a leak into the manifold - depending on how seriously the engine manufacturer considers this issue, it will
directly affect the cost of maintenance and life expectancy of the engine. Engineering this part is one of the most
expensive and critical parts of marinizing. It is VERY expensive and, not surprisingly, where many marine engines are
deficient. A jacket water cooled aftercooler is almost totally reliable, but maximum horsepower available is limited
because it can't cool as much as a seawater aftercooler.

5. A marine-specific cooling package must be engineered and installed. The cooling package must include a heat
exchanger, coolant surge tank, Seawater pump and plumbing, a transmission oil cooler and engine lube oil cooler.
Engines that already incorporate jacket water engine oil coolers are very easy to adapt to keel cooling, although keel
cooled engines require ENORMOUS transmission oil coolers because the return water from the keel cooler is only 15 -
20 degrees cooler than the what came from the engine.

6. Marine grade, moisture resistant starters and alternators are specified. To make the engine's packaging dimensions
more compatible with a boat engine compartment, the locations of the starter and alternator are often re-engineered,
requiring new brackets and different flywheel housings. The entire electrical wiring, circuit protection, harness and
connector system and instrumentation must be re-engineered for marine requirements.

7. Marine engine mounting engineering and mounts must allow maximum flexibility for installing the engine with its
centerline over, under, parallel with or at an angle to the stringers. Then you have to be able to reach the bolts.

8. Additional accessory drive capability must be added to allow for the installation of extra alternators, emergency fire or
bilge pumps, hydraulic pumps, or refrigeration compressors.

9. Belt guards compatible with accessory drives must be installed.

To the degree that a particular marine engine builder addresses these issues, they acquire a better or worse reputation
for their engines. That assumes they started with a good engine to begin with.

The best marine engines utilize heavy-duty industrial base engines, typically used in agriculture and construction
industries. These engines all have replaceable wet liners and very robust construction that allows very long life (typically
40,000+ hours) and economical rebuilds - this is vitally important to commercial customers who will accumulate over
8000 hours per year of running time if their application runs 24/7. <That type of construction is completely unimportant
and needlessly expensive in a pleasure boat application that is lucky to run over 200 hours a year.







Via iPhone.

manyboats said:

My foggy memory of the 50s says that the only pleasure boats that had FWC were 50 footers or thereabouts. Most engines were flathead gasoline and SWC.

In my 1953 Motor Boating magazine there is a full page ad for Crysler's "Crown" engine. It may be the straight eight because they talk about it's smoothness in the very extensive text .. but no mention of FWC.

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Hi Eric
The Chrysler Crown engine was based on the 6 cylinder T120 block.
The Chrysler Royal was a straight 8 cylinder, I don't know the block model.
Ted

Lots of years experience in this thread. What was the norm in the old days is definitely outdated now.

Engines gas or diesel that could run on SW cooling then are not able to now, (unless you find an old dinosaur in the bone yard) since on modern engines the differences in turbos, aftercoolers, intercoolers and different metals in the blocks preclude salt water and minerals. If you have an 'old' diesel it is possible to run straight salt water through for cooling. But any newer tier 2,3,4 diesels with after, inter or turbo cooling with aluminum coolers must have high efficiency coolers. In addition, These MUST have the high performance antifreeze, coolants used in the fresh water side. Salt water has way too many particulates that generate slime and growth almost immediately which degrade the heat transmission rate.

Keep in mind that the raw water cooled oil heat exchangers are an integral part of the overall engine cooling. The oil cooler sees the coldest water and takes a lot of heat out of the engine. Changing that to engine coolant cooled would likely raise the overall oil temp and likely necessitate a larger main heat exchanger. My BW manual states 190 max oil temp. My BW oil temps run 150 normally. My Lehman 135's spec oil temps of 165-220 and they run at 190. These temps are easily checked and at the temps I'm seeing I can be confident that they are where they should be for long life.

Ken

kchace said:

Keep in mind that the raw water cooled oil heat exchangers are an integral part of the overall engine cooling. The oil cooler sees the coldest water and takes a lot of heat out of the engine. Changing that to engine coolant cooled would likely raise the overall oil temp and likely necessitate a larger main heat exchanger. My BW manual states 190 max oil temp. My BW oil temps run 150 normally. My Lehman 135's spec oil temps of 165-220 and they run at 190. These temps are easily checked and at the temps I'm seeing I can be confident that they are where they should be for long life.

Ken

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Yep.

kchace said:

Keep in mind that the raw water cooled oil heat exchangers are an integral part of the overall engine cooling. The oil cooler sees the coldest water and takes a lot of heat out of the engine Ken

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Ken

I don't know the exact timing, but a decade or more ago some marine engines started going to jacket water engine oil coolers. This eliminates the chance of salt water entering the engine oil. Also it keeps the oil temps in the 190F degree range even at low RPMs, which hastens burning off volatiles, condensation and helps to permit 400 hour book oil change intervals.

sunchaser said:

Ken

I don't know the exact timing, but a decade or more ago some marine engines started going to jacket water engine oil coolers. This eliminates the chance of salt water entering the engine oil. Also it keeps the oil temps in the 190F degree range even at low RPMs, which hastens burning off volatiles, condensation and helps to permit 400 hour book oil change intervals.

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Interesting. Where can I read up on those?

Ken

kchace said:

Interesting. Where can I read up on those?

Ken

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Rainda Industries makes them (plate HXers) for various engine builders. My Perkins Sabre engines have them as does the Cat 3056. These have been in use for a long time. I seem to recall seeing them (or similar) on Deutz and MAN engines.