Repowering with a Tractor Motor

[janice142]

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

 

[stubones99]

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.

 

[psneeld]

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!

 

[Northern Spy]

Out of curiosity, what grade of stainless steel is your heat exchanger made out of?

 

[FF]

Why the heat exchanger complexity when a keel cooler cuts the parts count and works fine?

 

[kulas44]

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.

 

[oldhatt]

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.

 

[kulas44]

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.

 

[Nomad Willy]

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.

 

[Ski in NC]

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.

 

[janice142]

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.

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.

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.

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.

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.

 

[psneeld]

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....

 

[Northern Spy]

I'm only more confused.

Actually, Janice, I meant what kind of SS is the the "manifold".

 

[kulas44]

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 $$$$

 

[DavidM]

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

 

[Nomad Willy]

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?

 

[Marlinmike]

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.

Why the heat exchanger complexity when a keel cooler cuts the parts count and works fine?

 

[Nomad Willy]

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.

 

[kulas44]

Get the book !!!!!!!!!

 

[FF]

"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.

 

[kulas44]

The manifold, water cooled or not, makes no difference as to hours of useage or ambient temp. As to winter weather the watercooled manifold would actually help by adding mass and waste heat to the system. The only reason to not use a watercooled exhaust manifold is to try to save $$$$. Bad idea.

 

[Nomad Willy]

As for getting the best power for her boat David's idea is supreme.
There must be millions of sailboats in FL so little diesels like Yanmars no doubt are plentiful and cheap. I see them all the time on Craig's List even here in the PNW.

But doing something one's self holds adventures and attractions not found in traditional methods and equipment. The satisfaction of accomplishment by doing things like powering a small boat and getting acceptable results by methods and routes not commonly followed by traditional ways and established industrial methods.
I remember seeing years ago numerous big rowboats powered by lawnmower engines .. Sometimes w belt driven propeller shafts. In Alaska I've see Eskimos pick up an OB discarded by white men and found behind a log on a beach. You'd find them soon flying across the bay w bits of wood or ivory substituted for metal parts. Working fine for awhile .. probably not for long. But telling the Eskimo he's not doing it right won't even put a dent in his smile.

But learning the best and most propper way to do things holds it's potential satisfaction too. The expression "proud of a job well done" comes to mind. Certian personality types lean toward naturally looking for tried and proven ways.

I digress as usual but Janice has options to do it her way .. whichever that is. Just getting the job done w the best possible results would IMO be to follow Daves recomendation of finding used and installing it in the best traditional manner.

She asked for our opinions. I couldn't even figure out what the thing in her picture was for awhile. I was looking for pipes leading to cyl head exhaust ports on the side of the head of an engine at first. Interesting shape I thought and it was an instant puzzle. It was fun figuring it out. Perhaps it is a fun project fot her or she may be frustrated just trying to beat the high buck traditional route. There's a little inventor in most all of of us that needs to come out.

Where Janice is on this curve I don't know. But I'm sure we won't find her at either end but somewhere in the middle. Perhaps she posted it basically as probable entertainment for us. She probably knew we'd jump on it and flood the thread w ideas. So now we've had our fun and she has more options from Gerr and doing it according to "Hoyle" and best engineering practices to totally "wing'in it" and following the call of "I've never seen it done that way but I'll bet it will work". The latter opening the door to more unknowns, trouble, fun and perhaps even grief.

David's idea to do some shopping and perhaps bargaining to acquire the best fully engineered unit (probably would include the gear) would be best IMO but still gear ratios re prop clearance, exhaust routing, engine mounting ect would present considerable DIY engineering possibilities. And likely food for thread talk.

But now that she has this tractor engine David's option may no longer be open. Janice probably put the repower question to us too late. So it's just a question of riser. Still food for ideas.

But if digging out of a hole getting Gerr's book is bound to help.

 

[Off Duty]

subscribed.

 

[oldhatt]

some terrific feedback from willy, dave, kulas and the others. my hunch is that she got a decent deal on the kubota diesel and that the locals in carrabelle are trying to make it work for her as best they know how. i really hope that they know what they are doing. this is the SECOND diesel engine replacement that they have done for her in less than a year and i suspect that her pocketbook and her heart could not stand another failure.

 

[kulas44]

Bonefish Charley told me about the new boys taking out charters for bonefish in the Bahamas. He said "day tink day no cause day dont no e'nuff ta no day dont no". My thoughts are that other than being absolutely beautifull and very educational, this "riser" will turn out to be only that. I cant recall the many times that I have done projects that turned out to be total failures, mostly because I dont want to recall. Lots of times they took on a life of there own, going off on a tangent. Some were expensive past 5 figures. Nowadays I tend to look at a boat system and think "Why is it done like that" then do a lot of research. Its usually done that way for a reason. And, along the way during my research, I find lots of other ways to do it. Knowledge is the key. There is no end to folks that will take your money and do whatever you ask (some good some not so good) and not really care if what you are trying to do is workable.

 

[DavidM]

I have refrained from commenting on that beautiful piece of stainless for fear of offending Janice and throwing a wet blanket on what is an interesting exercise. But Eric's kind words have given me some cover, so here goes:

Marine engine builders learned a long time ago to use a water jacketed exhaust manifold (although Yanmar had to relearn that lesson with their BMW derived BY line of marine engines). If you don't water jacket that hot piece of metal, it's gaskets will fail, it will heat up your engine room and it may become a fire hazard. Very few builders don't water jacket them.

I appreciate that Ski has set up small diesels with non jacketed manifolds and they worked. Non jacketed manifolds might work in a big engine room with lots of clearance and ventilation. But for my money it just isn't worth the risk. Again ask Yanmar how their BYs worked out for them. There is a reason that the two biggest small marine diesel manufacturers use jacketed manifolds: Yanmar and Volvo and almost all marinizers like Beta Marine and Nanni.

It is the water jacketed exhaust manifold that dooms many DIY marinizers. It is a complex casting that just can't be duplicated in a one-off situation. The water jacketed manifold is the one item that makes a new Beta Marine engine cost twice as much as a new tractor Kubota.

The design of that stainless steel cooler is a disaster. All you need is a water injection elbow to do what that stainless cooler claims to do. The injection elbow was perfected many, many years ago for marine engines. It does need to be designed properly, installed with enough elevation and oriented so that the water flows downhill. There are many OEM and aftermarket injection elbows that can be bought relatively cheaply. The small Yanmar's elbow costs about $500.

I would much rather see Janice use a keel cooler and a dry stack exhaust than that stainless contraption. But the lack of a jacketed exhaust manifold is the real killer.

David

 

[Northern Spy]

I have refrained from commenting on that beautiful piece of stainless for fear of offending Janice and throwing a wet blanket on what is an interesting exercise.

The design of that stainless steel cooler is a disaster.

ditto.

 

[psneeld]

Wow....between the new input from experienced guys and some side chatter saying exactly the same thing plus my reservations on the "why that way?".....


Janice...seriously consider running the job so far by another firm...if at all possible.


I just don't think you want to go through this again and if this is job 2 for the same place....what went wrong with diesel number 1?

 

[janice142]

I'm only more confused.

Actually, Janice, I meant what kind of SS is the the "manifold".

The pipes for the exhaust are Schedule 40 (stainless)
The box itself is thick (and I'm drawing a blank at the exact measurement) -- I know the number, but it's been a long day.

 

[janice142]

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.

Got that covered. A brace will bolt to the aft end of the engine -- it's been mocked up and will be torch cut (the shrimp boat next to me is a welder -- steel boat/has to be) so he'll cut the metal to support the stainless.

I was concerned about vibration too... more for noise than anything. When the new holes are drilled for the engine mounts -- of course this was designed/built prior to the engine being set in it's final place. So it didn't fit -- bulkhead issue!

To solve that, a flex plate was added. That inch was all we needed to make things fit. It's a boat, right?

But now that the motor mounts have to be re-drilled I'll investigate adding some cushioning under the mounts to help deaden the sound. I've got some stuff her that might work

Thanks for the head's up about lag. That sounds similar to the asbestos tape used back in the day...