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Old 03-11-2015, 10:29 PM   #21
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Marin,
Mike at harbor Marine is the expert in the BW department.
Call him.

I always thought cooling tx fluids w engine cooland was stupid as they run the same temperature. How much heat are you going to exchange? Noticed that years ago on cars cooling tx oil w engine coolant in the radiator. Seemed stupid to me then too but there must be a reason for it. David?
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Old 03-11-2015, 10:42 PM   #22
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My salt water cooled volvo MS17D engine and MS-2 gearbox recently were recently replaced after I found water in the engine oil. I didn't even bother chasing down the source of the problem. It gave 33 years of good service, but I think one can not expect these components to last much longer than this.

I considered keel cooling when I first bought the boat, but I felt since the engine already had 30 years of contact with salt water, it would have been a big investment when the damage had already been done.

The Volvo MD17 was one of the few engines that were purpose built marine engines with salt water cooling in marine. They were heavy walled with plenty of corrosion allowance. I doubt if most modern day engines would last 33 years with salt water flowing through them.
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Old 03-11-2015, 10:48 PM   #23
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Cooler is not necessarily better. You want the lube oil temp in a certain range, and usually the tighter the range, the better. The advantage of cooling gear or engine oil with coolant is regardless what the load or sea temp is, the fluid stays in a fairly narrow temp band. Cooling with sea water means at low load and cold sea, the lube temp gets very low.

Gears do not make much heat, so even a modest cooler with 180F coolant will keep it happy. And I don't think that 190F number is a hard limit. The BW uses innards basically the same as an automatic tranny that can easily run at 250F.

One BW behind a Detroit 453 has been shrimping and oystering here for over 45years. It runs about 200F as the keel cooler is a bit undersized. As far as any of us can tell, the gear has never had any work done on it. No hour meter.
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Old 03-11-2015, 11:03 PM   #24
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My Perkins Sabres have coolant cooled oil and raw water cooled transmission fluid. If there would be a problem with too cool a transmission that would be a first in my memory. But, maybe someone has a story to tell.

So I'm in Marin's corner, we both boat in cold water and a 115F transmission is normal for me at a 30% engine load. Still plenty hot enough for ATF to be flowing easily. BTW, stock coolers on my transmissions are designed for warm Middle East water to keep the transmissions below 160F or so at full load.
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Old 03-11-2015, 11:03 PM   #25
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Borg Warner manual; Page 16; Series 70, 71, 72, 73 transmissions:

"Better efficiency and extended gear life will result when the transmission sump temperature is maintained between 140F and 190F or 60C and 88C. Transmission pressures are dependent upon cooler flow. It is important to select a cooler which has suitable flow characteristics as well as proper cooling capacity. Cooler back pressure affects line and cooler pressure. low cooler pressure after an extended period of hard running indicates the need for a cooler which has more cooling capacity and possibly more back pressure. High cooler pressure after an extended period of hard running indicates the need for a cooler which has less back pressure."


When in doubt follow the manufactures directions!!
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Old 03-11-2015, 11:07 PM   #26
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I`ve seen Lehman 4cyl 80s that were salt water cooled, no exchanger. Lots of shell came out when the broker started them, he told me it was running hot and needed cleaning out. How would that be done?
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Old 03-12-2015, 12:12 AM   #27
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It's strictly a matter of economics. It wasn't too long ago that straight salt water was used for engine cooling (directly through the blocks) and reduction gear (transmission) cooling was as cheap as possible. Now with other priorities included it makes more sense (since you have more cents) to install a heat exchanger and/or a keel cooler. Not everyone has the cash to do the 'right thing'. Heck... It wasn't too long ago that stainless was not an option for anchors too. Just depends on the finances.
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Old 03-12-2015, 12:14 AM   #28
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I have debated that exact subject on a few other forums. What if,,,,,I raw water cooled a Cummins 6b 120 hp engine. How long would it last. Of course I would need a 140 thermostat. The 6B is a parent bore block (AKA a throw away) so no liners to be concerned about. Chevy small blocks were RW cooled and stood the time test very well, if you kept up with exhaust risers. The really interesting thing is that all the guys in the "know" are appauled at the mention of the idea and all say it wont work. And then have absolutely no knowledge, first hand or otherwise, as to why. If a 6B cummins would last 10 years with raw water cooling in salt water that would not be to bad. I can buy a rebuilt long block for about $2500. It would be VERY easy to cool a 6BTA, even at 370 hp, with raw water. In higher hp the problem has always been cooling related on the 6B series. The 6BTA is capable of 450 hp sustained but its cooling system is not even close to that. Raw water cooling is. Someday I'm gonna do it. I have a pair of 6Bs and a 40 foot hull that I would love to turn into a workboat/fishing boat type. I need more time !!!
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Old 03-12-2015, 01:40 AM   #29
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One of our good friends still has and uses the boat his father bought new over 50 years go. It is a 28' Richardson. Two Graymarine gas engines, raw (salt) water cooled. Both engines are still running great.

BTW, the BW Velvet Drive manual that came with our 1973 Grand Banks sets a hard limit of 190 degrees maximum operating temperature (anything over may cause damage and the ATF must be immediately replaced, according to the operating instructions) and gives no temperature envelope or minimum operating temperature.

So like the FL120 itself, the do-this, don't-do-that instructions in Velvet Drive manuals seem to vary with whoever was writing the manual on any given day.

Since we have all the original operating, service, shop and parts manuals that were delivered with the boat in 1973, we have elected to follow the manufacturers instructions or specifications as called out in those manuals.

I've never had an engine or transmission specialist tell me I will damage an engine or a transmission by following the manufacturer's operating and service instructions for that engine or transmission, so we figure if we do that we'll get the maximum service life out of the thing that it was intended to have.

So far, that seems to be the way it's panned out be it vehicles, boats, or planes.
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Old 03-12-2015, 03:09 AM   #30
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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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Old 03-12-2015, 05:25 AM   #31
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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?
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)
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Old 03-12-2015, 07:45 AM   #32
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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?
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.
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Old 03-12-2015, 09:09 AM   #33
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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.
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Old 03-12-2015, 09:49 AM   #34
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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.
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Old 03-12-2015, 11:14 AM   #35
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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?
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.
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Old 03-12-2015, 11:58 AM   #36
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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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Old 03-12-2015, 12:41 PM   #37
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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"
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Old 03-12-2015, 12:46 PM   #38
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For the record, it's not an "explosion." It's combustion. Big difference.
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Old 03-12-2015, 12:53 PM   #39
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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.
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Old 03-12-2015, 01:28 PM   #40
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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?

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.
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