Raw-water to fresh-water cooling conversion

[Catamount]

Alan,

I think we would call that insulation.

My father-in-law has a Maine lobster boat that had a dry exhaust that ran right up through the back of the wheel house. Even with lots of fiberglass insulating tape wrapped around it, you still wouldn't want to touch it. Great boat for winter-time fishing, I suppose.

Regareds,

Tim

[Catamount]

Just so everyone can see what I'm talking about, here are a couple of pictures of my engine (exhaust side):





(note that there is no vented loop before discharging to the exhaust mixing elbow, and I'm told that there should be one.)

Comments welcome!

[windthief]

Well with the four companies that I am a dealer for seakamp,sen-dure, san juan, and bowman at least two of them will not advise freshwater cooling an engine or manifold after salt water imersion.
When I first called Brad at san juan for a custom build fresh water system and explained that it was going on and older salt water engine he told me that my customer was wasting his time. His explination to me was the same as my earlier reply. Now being in business, the both of us, we are here to make money and secondly make sure our customer get what is expected from a product. I never try to NOT make money or turn away customer who want to spend a thousand dollars with the company. Likewise, if I turned away my customers on the premise of false information I wouldn't be in business. My feelings are not hurt if a customer leaves the store upset because he or she believes different. I do sleep better at night though.

I deal alot in cast iron both gas and diesel, in fact i just unloaded 2400lb of the crap and will have it sold in less than two months. People come in on a regular basis who have boiled, rodded, acid bathed, and otherwise wasted their time just to buy new equipment. Enough said?

like I said before you will get very limited advantages to now freshwater cooling your engine. Your manifold is no longer available unfortunately and really from the looks of it if you acid bathed your manifold it would fail in short time. I would spend my time locating one out side of Yanmar or look into having something custom build.

to each his/her own.

[Alan Wheeler]

OK, so you have got the water cooled Manifold. That can easily become fresh water cooled. All you need is a heat exchanger and you don't need anything huge. Get your hands on what ever you can find that suits the room you have. Yes, surface area of heatexchanger has a major effect on cooling, but so does the volume of seawater being pumped through. So you have a bit of a fudge factor with either way, so don't panic about the size of the HE, especially on the small side of the argument.
The only concern I see is your cooling water entry to the riser. It's on the wrong side of the Elbow. It should be on the other(downside) of the elbow. This is so water doesn't run back into the manifoldwhen you shut down. At the mo, you will have water run back and sit in the manifold. Best scenario is it will condensate from engine warmth and can enter valve seats and corrode, worst scenario, actuall water could flood cylinders. It is that riser that would normally run dry and that I suggested should be heat insulated with lagging so as it is not dangerousely hot.
You don't need a vented loop in the cooling discharge pipe. That is for breaking siphons. The cooling pump will be a shut off valve when it is not rotating, so no siphon could exist if it could anyway.
If you wanted to spend a bit of time, a good cleanup and paint of all the exterior would make a world of diference. and don't be afraid to spray plenty of WD40 or better lubricant around any moving parts like throttle connections.

[windthief]

[QUOTE]Alan Wheeler once whispered in the wind:
[B]The only concern I see is your cooling water entry to the riser. It's on the wrong side of the Elbow. It should be on the other(downside) of the elbow. This is so water doesn't run back into the manifoldwhen you shut down.

If you don't know a part you shouldn't comment on it. The water fitting on that Yanmar mixing elbow 124070-13520 is only the point of introduction to the unit itself. The water doesn't actually mix with the exhaust until the downward side of the loop. Your theory is correct your product knowledge is a little lacking.
by the way this elbow is still very available as it is used on many new Yanmars.

P.S. if your engine is ever on any tack or point of sail under the waterline you will need no install a siphon break in the water line between your manifold and the mixing elbow.

[Alan Wheeler]

Wow up there Bradley, I suggest you take a chill pill. A little Politeness can go a long way.

[Alan Wheeler]

So lets look at this again Bradley. Firstly, let me qualify myself. I am NOT AN EXPERT. So maybe that's why I don't have a lot of product knowledge on a Particular part. But thanks for the clarification. Right, onto the topic.
So have you ever verified that a problem can occur, exists or what have you, with converting from Raw water cooling to a closed circuit fresh water system?? Have you ever been able to detect Salt in the system after it has been totally flushed? What proof do you have that it is an issue?

Now with the Siphon break, how exactly is it going to siphon? When the pump is not turning, the impellor of a water pump is a dead stop to the water flow. This is assuming a rubber impellor positive displacment pump is being used. The only other pump I can think of that maybe used and that could be free flowing would be a centrifugal type and they are not commonly used for water cooling. The only place water can get back to the motor is via the exhaust. Usually a Goosneck is used for installs where the exhaust and motor end up being below the waterline at some point.

[Catamount]

Bradley,

The point I read you trying to make is one regarding the cost-benefit ratio -- will the benefits outweigh the costs? This is a reasonable question to ask, one that we really should discuss

So let's list the costs:

1) total parts less than US$500 (potentially a lot less, depending on how successful I am at scrounging used parts)
- heat exchanger <$200
- pump <$200
- expansion tank $12 (used auto part)
- thermostat ~$30(?)
- hose and fittings <$50

2) time and effort in rounding up the parts, installing system, figuring out how and where to mount everything, etc...

3) some extra weight to carry around in a somewhat weight-sensitive ex-racing sailiboat

4) added complexity to systems -- additional pump to maintain, heat exchanger to periodically clean out, more zincs to replace, etc

And what are the benefits?

1) reduce the potential for further corrosion of engine and parts, potentially extending life of engine

2) eliminate the further deposition of scale in the engine and parts (although now it will take place in the heat exchanger)

3) easier winterization (engine is already full of antifreeze, just need to drain or winterize raw water side)

4) higher engine operating temperature, which is supposedly more efficient --although I don't totally understand this yet. Is this really such a good thing?

Are there costs or benefits that I've left out? Have I over- or under-stated any of the costs or benefits?

If I'm reading your comments correctly, in your opinion the benefits do not outweigh the costs for an older engine like mine that has been run on raw-water cooling for so long. Presumably this is because the extent of corrosion that has already occurred is such that converting to FWC at this point really won't do much to extend the life of the engine. Is that a fair characterization?

Personally, I don't know the answer. You may very well be right. On the other hand, I've read a lot of "authorities" arguing in favor of FWC conversion (not just in this forum). I will continue to investigate.

the four companies that I am a dealer for seakamp,sen-dure, san juan, and bowman

As a dealer, even though you are advising against it, can you send me a price quotation for a Sen-Dure 2A20-1-7-V-V heat exchanger or an equivalent unit from one of the other makers? (2" diameter shell, approx. 20" tube bundle length, single pass, Cu-Ni alloy, 1/2" NPTF fittings, although the exact fittings are not all that critical.) I am also interested in a Jabsco 2760-0001 pump or similar. You can e-mail me directly at: catamount@nh.acadia.net. Thanks!

Regards,

Tim

[windthief]

No pun intended.
Sen-dure is closed right now and they don't
list your custom request in their regular pricing.
I'll get back to you tomorrow with the pricing from sen-dure and sea kamp.1 3/8" water size as I decipher your supplied part number. Is that correct?

[Catamount]

Hi Bradley,

The price list I downloaded from Sen-Dure's web site, a PDF file which is dated 1/30/04, lists part # 2A20/1P7 at $215 on page 22. This doesn't describe what fittings the exchanger comes with, though.

The heat exchanger itself is a "Typical Stock Exchangers" as listed on page 1 of the Sen-Dure catalog (another PDF file I downloaded from their web-site) under Individual Heat Exchangers, where they give an example of the part number call out.

2A = diameter of shell (2")
20 = bundle length (20")
1P = one pass
7 = Cu-Ni alloy
V = 1/2" female NPT shell side fitting
V = 1/2" female NPT tube side fitting

Again, I'm not particular about the fittings.

Regards,

Tim

[GordMay]

Submitted FWIW, & without comment ...
From the Atomic-4 FAQ’s http://www3.telus.net/Atomic_4_Eng_S..._Questions.htm

Q. Is it a good idea to convert my raw water cooled engine to fresh water cooling by fitting a heat exchanger?

A. Yes. The cast-in water jackets in the cylinder block, cylinder head, and exhaust manifold of raw water cooled engines run in salt water are gradually being corroded by the salt water even when the engine is stopped, and plugged by the minerals and salts precipitated out of the hot water as the engine is run. Usually the first problem that occurs is overheating because the partially plugged water jackets restrict the flow of cooling water, and then later the engine block, cylinder head, and exhaust manifold begin to corrode through until they are so weak small leaks or cracks develop. Although cylinder heads and exhaust manifolds can be replaced, it is very expensive to replace the engine block itself (Atomic Four engine blocks are no longer available). The cost of all the components necessary to convert an engine to fresh water cooling is approximately $900, and although the conversion is expensive, it is one of the few modifications you can make to your engine that will actually increase the value of the boat, since it is quite common to see a boat with a fresh water cooled engine advertised at $500 to $1,000 more than the same model/year/condition boat with a raw water cooled engine.

When a raw water cooled engine is converted to fresh water cooling, the existing water pump (usually driven directly off the engine from an engine auxiliary drive) is usually used as the engine coolant pump to pump the water/antifreeze coolant through the engine, to the heat exchanger, and back to the engine. 2 types of heat exchanger can be used, a horizontal engine mounted heat exchanger mounted over the exhaust manifold or at the rear of the engine over the marine gear, or a vertical remote heat exchanger mounted on an adjacent bulkhead. Universal diesel engines after the Model 5416 were equipped with fresh water cooling as standard equipment, with the sea water pump driven by a power take-off on the front of the engine. The engine coolant pump on these models is a centrifugal belt driven automotive type water pump. Universal Atomic Four engines were available with an optional fresh water cooling system which used a horizontal heat exchanger mounted over the exhaust manifold and a rubber impellor sea water pump mounted over the starter and driven by a belt from a pulley on a power take-off assembly mounted on the front of the flywheel. Aftermarket heat exchanger kits mount the sea water pump in various locations: over the starter in the same configuration as the OEM system, over the alternator and driven by a longer alternator belt which also still drives the alternator, directly off the front of the engine using a rubber cush drive assembly, and an electric pump mounted in a convenient location near the engine or heat exchanger and used as an engine coolant pump so the original rubber impellor pump can be used as the sea water pump (electric pumps have a hard impellor which must only be used with clean coolant... and because they are not fitted with a rubber impellor they are not self-priming, which is a requirement for any sea water pump.

We recommend the OEM factory sea water pump configuration, which is a sea water pump mounted over the starter and driven by a belt running off a PTO mounted on the end of the crankshaft. This configuration requires 3" clearance in front of the engine flywheel cover, which in many cases can be obtained by cutting a bit out of the engine cover, or remounting the engine cover/cabin stairs slightly forward. The factory installation also had a horizontal heat exchanger mounted over the manifold, however some smaller sailboats do not have room for this and a horizontal or vertical heat exchanger must be mounted on an adjacent bulkhead. The OEM sea water pump was a Sherwood R30G...we use a similar pump... a Jabsco, because the Jabsco is cheaper, easier to get parts for, and easier to service. This arrangement is much superior to any other configuration except direct mounting the sea water pump on the end of the crankshaft (which requires space for the pump and rubber cush drive... about 8"... usually only available on engines fitted with V drives where the engine faces the stern) because it allows for easy access to the pump, doesn't require that the stock alternator belt carry the extra load of a water pump (and therefore allows the stock 35 amp alternator to be replaced with a higher output alternator without increasing the belt width (there is limited clearance for a pulley larger than the stock auxiliary drive pulley... and 90 amps is the limit for the stock belt). If you order a fresh-water cooling system installed during an engine rebuild we will mount the heat exchanger on the engine in the OEM configuration (longer manifold studs are fitted to all rebuilt engines to allow for heat exchanger mounting). If you find that the engine cannot be installed with the heat exchanger in that position, it is a simple matter to remove it from the engine and install it on an adjacent bulkhead (a couple of longer coolant hoses may be required... use automotive heater hose available from any auto parts store).
without comment ...

[Alan Wheeler]

Gord, mate, your a legend.

[Richhh]

an easy solution to your problem is: http://www.moyermarine.com/cgi-bin/s...rebuilder.html
.... a heat exchanger package that proven for 35hp engines.
Its based on a 15 degree approach temperature with inlet cooling water at 80 deg. f. at a flow rate of 3 gallons per minute @ 2000 rpm. A 2QM20 would max. out at 3000 rpm so the raw flow would be about 4 gpm. Flow is countercurrent - the engine cooling water is flowing in the opposite direction of the raw cooling water. Sorry I dont know the surface area. Surface areas isnt the only consideration as surface area is derived from the operating conditions, the type of metal used, the expected fouling, etc. The above Heat exchanger is "U" tube bundle (cant be mechanically cleaned - chemical cleaning only) but has proven itself for about 15 years on Atomic-4s ..... which will have a wee bit larger heat output than a 2 cyl. Yanmar 2QM. At $563 for a total package its not a bad deal.

[NoTies]

Right, haven't read all the replies so may be repeating some advice.
First, find the operating specs for your engine. If they state the jacket temperature should be maximum 45deg C (usual on raw water cooling) then the piston to liner, piston ring clearance etc will be based on this. If you install freshwater cooling with a thermostat set at a higher temperature then you will likely have problems with piston seizure. I have had to correct a problem exactly like this on a Yanmar genset (45kW I think) in the past. Not cheap.

[Catamount]

Thanks for the warning!

FWIW, I have acquired a heat exchanger with integral expansion tank and appropriately-sized jabsco pump for US$170 shipping included. Now I just have to figure out how to mount everything, then connect the plumbing and away we go...