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Old 05-18-2015, 01:07 AM   #1
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Repowering with a Tractor Motor

I'm in the process of repowering, using an inexpensive 18hp Kubota tractor engine in my trawler. Marinizing the cooling system is the latest piece published in the series about the process. If this subject interests you, the article is here:

Janice142 article Marinizing the Cooling System of a Tractor
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Old 05-18-2015, 07:08 AM   #2
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Janice,

My ideal trawler would be a Bruce Roberts steel trawler with two Deutz 912 engines. It would have to be re-manufactured engines since Deutz no longer makes that engine. They are air cooled, so you don't have to worry with cooling water, anti-freeze, and a few less holes in the bottom. You do have to worry a little more about airflow in the engine room, but to me that's common sense.

In the winter (outside FL), the cooling air from the engines can be ducted around the boat for heating. It's already blown by the turbine fan on the engine. All you have to do is make sure you have a good exhaust system.

If you need hydraulics, on the opposite side of the engine from the Bosch injection pump, there is a mounting plate that can be replaced for either a single or double pump, geared directly off the engine timing gear. That will give you up to 10.4 gpm at 2000 psi hydraulic oil pressure, if you need that for steering, thrusters, windlass, stabilizers, davit, etc.

Back in 1978, the last time I was in the business, I overhauled a 4 cylinder 914 Deutz powered irrigation pump. That pump engine finally needed another overhaul after over 50,000 hours of operation.

Deutz used a cast iron block with cast iron cylinder sleeves with aluminum heads. Each sleeve and head is separate, much like today's Lycoming aircraft engines. That means a top end overhaul can be done in place. If the oil was changed reliably, you almost never needed to do a bottom end overhaul.

Btw, Deutz engines are incredible on fuel economy, burning half of what a Cat, Cummins, or JD consumes. The newer engines have gotten better economy, but still no where near Deutz.

BTW, the Deutz engines were what powered the German tiger and panther tanks in WWII, and didn't have to worry about getting their radiators shot out like the Sherman tanks did. The older Deutz engines (pre-1967) had indirect injection which ran much smoother and almost sounded like a gasoline engine, since they lacked the loud knock of today's diesels. They were not quite as powerful or efficient, but was smooth running engines.

BTW, be wary of Lombardini / Deutz engines found in track loaders and excavators today. They have some of the efficiency, but are water or oil cooled. One engine design they did always leaked water into the oil, so they made it all oil cooled.

So, don't be afraid of a tractor engine. They are designed to be tough, and with the exception of not having the salt corrosion problems of boats, a tractor has a far harder life.
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Old 05-18-2015, 07:33 AM   #3
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Not sure I would duct straight cooling air into the boat...maybe an air exchanger might work.

Not too many enjoy the smell of an engine room all the time.

Janice - what does the shop think about heat gain or loss with this?

I am guessing this is the heat exchanger too?

The raw water flow is enough to overcome the exhaust temp input gain to the coolant?

Pretty cool if it all works as designed!
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Old 05-18-2015, 07:49 AM   #4
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Out of curiosity, what grade of stainless steel is your heat exchanger made out of?
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Old 05-18-2015, 08:04 AM   #5
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Why the heat exchanger complexity when a keel cooler cuts the parts count and works fine?
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Old 05-18-2015, 09:11 AM   #6
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You are correct, those welds are magnificent. However, I would not have designed the raw water injection point inside the manifold. I know, stainless is very corrosion resistant, but seawater injected into a HOT exhaust stream is even more corrosive at the point of injection than the best stainless can handle. Thats why everyone else makes the "mixer" removeable/replaceable. Also being inside the manifold, a leak will put saltwater into your cooling system. I would build an external mixing elbow, preferably as high as the engine room allows. Insulate "lag" the dry up going side and water cool the down going side. Gerr's fine book has all the info.
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Old 05-18-2015, 10:45 AM   #7
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i really like what janice142 is doing with the diesel kubota tractor engine. i do not really understand the physics or the engineering as much as i would like to, but the concept is great. i have had traditional diesels in my boats for just shy of 40 years. they always demand relentless devotion to care and maintenance. what she is doing may in some ways allow her to beat the system by enabling her to re-power and invest maybe only one third of the cost of a regular marinized engine.

some nice ideas and questions have already been expressed in this thread. janice may be providing a blue print for any of us who may be facing engine replacement some day. i hope it works well for her and i hope that she provides periodic updates as she cruises the gulf coast of florida.
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Old 05-18-2015, 11:09 AM   #8
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I think, after looking more closely, that I may be confused as to the purpose of the "manifold". Is this the actuall peice that bolts directly to the engine and its 3 exhaust ports, or is it a fresh water cooled exhaust riser, with an injection point ? The engine looks like a D series Kubota, maybe a 750,850,950, etc. If so cast iron fresh water cooled manifolds are available and not overly expensive. They will last as long as the engine, being cooled by the same liquid. That being said, I like to fab my own, usually with 304 SS. But, paying a fabricator would not be economical over the factory manifold. If indeed this is the "riser you will still need a manifold, correct ? Its not considered best practice to use a "dry" exhaust manifold, even with a water cooled riser.
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Old 05-18-2015, 11:29 AM   #9
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Kulas44,
Isn't this just a riser/cooler ? The engine must have an exhaust manifold plumbed w coolant .. as is typical.


Janice,
It looks like the flanged end attaches to the engine w studs or bolts. And only a two bolt flange not very wide or tall.
Small diesel engines vibrate a lot and if the manifold/riser/cooler is hard attached it will probably fail. Perhaps I'm missing something and it's not so.
Now looking at it more ...
Since the manifold is a cooler cooling the hot exhaust pipe the coolant will be heated in the box. So it will have at least a slight tendency to rise. Because of the inverted "U" shape the outboard end of the box w/o a coolant inlet may not circulate very well. Infeed coolant to both bottom chambers may be beneficial and would be simple to add.
Another thought is that the traditional "heat blanket" may be much cheaper and foolproof why the manifold. Perhaps I didn't read very carefully.
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Old 05-18-2015, 11:36 AM   #10
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I have set up little tractor engines for propulsion. I had no problem using the factory dry manifolds. Cummins uses a dry manifold on their marine QSM11, so there is a precedent.

Edit: Looked at the photos, that does look like too much mass to be supported only by the inlet end.

Seems like a good bit of hardware and complexity to do what a factory mixer accomplishes.
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Old 05-18-2015, 11:37 AM   #11
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Quote:
Originally Posted by stubones99 View Post
So, don't be afraid of a tractor engine. They are designed to be tough, and with the exception of not having the salt corrosion problems of boats, a tractor has a far harder life.
I've heard that too. One of the fellows here has the identical motor in his tractor. Running 1700 RPM he uses less than a quart of fuel per hour. And he swears it's dead simple to take care of.

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Originally Posted by psneeld View Post
Not sure I would duct straight cooling air into the boat...maybe an air exchanger might work.
Pretty cool if it all works as designed!
I've got blowers but those won't impact the engine room except to evacuate the air.

We need to cool the air exiting the engine. I cannot have a hot muffler in the middle of the bilge. The manifold with separate heat exchanger are designed to cool that temp down enough to make the run (3' forward though probably a 5' length of hose by the time the bend is done) to the water muffler, and then out.

As for the rest of your questions psneeld, I'll have to ask the mechanic. He is closed on Monday.

Quote:
Originally Posted by Northern Spy View Post
Out of curiosity, what grade of stainless steel is your heat exchanger made out of?
The heat exchanger is copper as I understand it. It's off an old V8 Mercury.

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Why the heat exchanger complexity when a keel cooler cuts the parts count and works fine?
I'm less enamored with keel coolers and like keeping the holes in my boat to a minimum. At present there are three. And too, I do check the depth on occasion with my bottom.

The sad thing is there is a sound the boat makes just prior to touching bottom. And I know that sound.

Quote:
Originally Posted by kulas44 View Post
You are correct, those welds are magnificent. However, I would not have designed the raw water injection point inside the manifold. I know, stainless is very corrosion resistant, but seawater injected into a HOT exhaust stream is even more corrosive at the point of injection than the best stainless can handle. Thats why everyone else makes the "mixer" removeable/replaceable. Also being inside the manifold, a leak will put saltwater into your cooling system. I would build an external mixing elbow, preferably as high as the engine room allows. Insulate "lag" the dry up going side and water cool the down going side. Gerr's fine book has all the info.
Hello Kulas44... Im trying to picture "insulate the lag" as that's what I do have albeit inside the box. You do have a point about stainless and corrosion. As I understand it, corrosion needs air and water and I've definitely got that. Even with something outside the manifold, I'll still have the same situation.

Have you an opinion on how long between failures I should expect? I was told this manifold was "lifetime" and wonder if it's the lifetime of a gerbil (two years) or a grey parrot (60 years) or something else.

Also, theoretically, were salt water to get into the heat exchanger, how would I know? Symptoms? And is that necessarily a bad thing? How bad?

The world we all strive for is ideal. The world I live in has compromises.

This is complicated and I'm only beginning to understand. I appreciate guidance, and thank everyone for their input.
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Old 05-18-2015, 11:44 AM   #12
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Sorry Janice the air circulation comment was for Stubones99.


If you have a separate heat exchanger...for the life of me I cant fathom the coolant cooled injection box. A jacketed injection elbow should be all you need if small for that engine....but a dry manifold also needs some kind of heat resistant lagging or protection...but without a photo I am just shooting in the dark....
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Old 05-18-2015, 11:46 AM   #13
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I'm only more confused.

Actually, Janice, I meant what kind of SS is the the "manifold".
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Old 05-18-2015, 12:15 PM   #14
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Lagging is a "boaty" term for insulation, usually some type of fiberglass. Car hotrod guys call it "header wrap", just a heat resistant material that comes in rolls of various width. You wrap the dry parts with it then coat it with Childers insulation and lagging adhesive (looks like milk . Most NAPA stores near saltwater carry all this stuff, or can get it for you. I am still confused about the terminology. As I see it this is an exhaust "riser, seperate from and bolted to the exhaust "manifold" correct ? If so vibration from the D series Kuboto will break/crack that 2 bolt flange in short order. All to do with the length and resonant harmonics. At the least you're going to need to weld some tabs on for support braces. Using the dry exhaust manifold is still not best practice but it can be "lagged" and coated and made serviceable. If in fact you do use the dry exhaust manifold a simpler (read more reliable/cheaper) method would be to just have your SS pipe riser fabricated as high as your engine room allows, lag everything and put you water injection shower on the down side. I REALLY suggest that you get and read Gerr's book before spending anymore $$$$
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Old 05-18-2015, 01:28 PM   #15
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I am curious. I suspect that you bought a used Kubota engine from Yanmar Tractor Parts. What did it cost?

A used but not rebuilt Yanmar 18 hp engine should cost less than $3000 with all of the marine stuff.

David
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Old 05-18-2015, 03:37 PM   #16
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Well she's got the engine and if see'in is still beliv'in she's got the jacketed riser/cooler.

Janice I'd just use it as I think it will stabilize the temps of numerous things. Obviously you've got room for it.

But the mounting flange must be changed .. will-na work. A wire mesh type flexable exhaust coupling insert of probably 3" w flanges on both ends and then warped w heat resistant "blankets" would probably work but not exactly cheap. But not expensive either. Cheap woulda be just 4 90 degree elbows and longer verticle pipes.

I personally like the water jacket idea and perhaps a ""V" shaped strut (or pair of same) could be fabed super easy and attached to the transmission. That may keep the riser/cooler from parting company w the exhaust manifold. Vertical support will be easy but lateral could be iffy. That's why I mention the pair of struts as in a "V". What is the exhaust manifold made of?
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Old 05-18-2015, 03:49 PM   #17
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Thinking the same thing, plus can be mount in a location that if touched bottom would have no issue. Pretty cool project all the best with it.
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Why the heat exchanger complexity when a keel cooler cuts the parts count and works fine?
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Old 05-18-2015, 08:22 PM   #18
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Another idea ....
Put a 90 elbow between the cooler/riser box and the exhaust manifold mounting the riser/box crossways or athwartships. Rigid mounting to keep the riser moving in sync w the engine will solve the mounting issue. Some changes in the wet exhaust run may be necessary.

Re the space in your boat this could be an advantage and a side exhaust may even become attractive.
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Old 05-18-2015, 08:47 PM   #19
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Get the book !!!!!!!!!
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Old 05-19-2015, 07:07 AM   #20
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"The engine must have an exhaust manifold plumbed w coolant .. as is typical."

Typical on white boats that run 100-200 hours a year but not on lobster or commercial boats that need to do 1,000 or operate in cold winter weather.
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