Date: 15 May 2015. Marinizing the
Cooling System of a Tractor.
Update. 21 May 2015. After speaking at length with
the mechanic this morning, I went back and corrected (below) the
drawings. I had the flow of water the opposite. Basically, water is
pumped into the bottom of the box and exits to the heat exchanger
out the diagonal. Also, the place where the raw water is injected in
my drawing was too high. It is much lower. Pictures a-okay as of
Further on this will be upcoming. I am relieved.
Still, I wanted to correct this article ASAP. J.
Transforming a tractor engine into a marine motor is not for
sissies. Fortunately, I have back-up and progress is being made.
My Kubota 18hp [from
Yanmar Tractor Parts] is a gem. And it is many thousands of
dollars less than the marine Yanmar motors so prevalent in boats today.
For the budget minded, that has a great deal of appeal.
Specifically, you can buy an 18 hp Yanmar marine engine with
transmission for in the neighborhood of $14,000. Plus installation
a place like
Yanmar Tractor Parts
for a different option.
motor adapted properly is a viable choice for those of us without deep
pockets. And yes, Kubota motors are comparable with Yanmar.
labeled marine therefore the
price is far more to my liking. Their factory marinized line
includes Beta and Universal.
tractor motor does add a level of complication. Cooling is an issue.
In that regard, the men at
Just Right Marine in Carrabelle along
with a welding shop in Tallahassee created for me a wonderful
manifold. Mine is 100% stainless (be still my heart!) and beautiful.
It should outlast the boat.
The welding that is magnificent. And no, I do not use that word
inappropriately. Check out the amazing work done by a Professional
(capital "P") at Tallahassee Welding and Machine Shop [http://tallawelding.com/]
Any welder who can produce seams like
this does not need a business card.
Simply a picture of work well done is more than sufficient.
(That's a temporary wrap of silver tape on the
Each person who has seen this
manifold has commented on the welding. Around the
Just Right Marine
store, everyone has asked
who did it, and how much. As for the who did it, contact Kenny Small
at 850-576-9596. And the time? Eight hours. There was a CAD
(computer drawing) involved too.
Daddy was a
welder. Heck, he even built the steel 40'er I grew up aboard. Still,
I will say without equivocation that the seams on this piece are as
fine as I have seen. Impressive is not too strong a word.
Details on the design can be found in the
Stainless Manifold Ordered (tractor motor
adapted for boat)
piece. That article goes into more detail. For your
convenience, I have copied the following box from that article.
Design for Tractor Motor Used in a Boat
My sketch could be better, so let me clarify a bit.
First of all, there's a heavy duty big stainless box that
surrounds the pipes. Those pipes (RED
ARROWS as seen above) carry the exhaust from the
engine. Fluid, a combination of anti-freeze and fresh water,
will fill said box. The solution will flow in from the bottom
left corner and exit the top right. That water/anti-freeze
concoction will go into (and come out of) a separate tank.
A sturdy stainless box encloses the Schedule 40 (heavy, thick
walled stainless) 1.5" pipe. The
STAINLESS PIPE carries hot exhaust air through the
cooling manifold box. A NIPPLE at
the top will deliver raw water into the pipe. That will further cool the
BLUE ARROWS AND STARS
show water and antifreeze as they flow through the stainless
box. There will be an external closed fresh water tank. That
unit is a Heat Exchanger.
Addendum April 2015: My
drawing is a bit off from the final result. The changes you will
note are the box (aka manifold) is now U-shaped. That will allow
better flow of the fluids through it.
Also, the coolant goes in at #1 and fills the box/manifold. That
coolant, a combination of anti-freeze and water, exits at #2. There is an upward flow of
cooling water being pumped through the unit.
Photo updated 21 May 2015.
Photo updated 21 May 2015.
Here's how the
designed manifold works: (the manifold is the U-shaped box)
below, the red arrows shown are actually a schedule 40 pipe
that the air flows through. I've tried in Paint to draw it and
Proof positive that Windows Paint and I do not always get
Photo updated 21 May 2015.
air exits the engine. That flange at the
far left bolts to the engine. There is a bracket under the
middle of the unit to support the weight.
Photo updated 21 May 2015.
Air flows through the Schedule 40 (thick walled) stainless pipe. (red
and white arrows, beginning on left) toward the exit of
the manifold on the right.
coolant enters the manifold at the
bottom right and exits through the diagonal on the left side.
It's fed by a pump. This will be
a mixture of antifreeze and fresh water. The coolant will fill
the box. The red pipe (see above) will be
surrounded by that mixture of anti-freeze and water.
water* enters the red pipe to add cooling
water to the hot air. The water and air will mix just prior to
of the manifold on the right via a hose. The raw water's sole
job is to cool the pipe so the hose won't deform from the
From there the Air and Water will flow through a
water muffler (to quiet the sound) and then out the side of
Seaweed. For those interested, it is a Vernier Lift Muffler. There will be no *raw water in my engine. That should
keep the components in good shape for a long time.
*Raw water is the water found outside the boat
(river water, ocean water, lake water, etc.)
This is my water muffler:
The water muffler (aka water-lift) is part of the cooling system. It
helps quiet the sound too. Water and air will flow through the
chambers in it, then exit out the starboard side of Seaweed.
Size is difficult to determine from this angle of the
Vernier lift is a bit smaller than a five gallon bucket. Small engine equals
small water muffler. The obverse is true as well, i.e. a larger engine
requires a much larger water muffler.
According to Brian on LCV (Low Cost
Voyaging on Yahoogroups), "As far as water-lift
sizing, the larger engine does not always have the larger muffler. The
inlet and outlet size is larger on the larger engine but the volume is
determined by the hose run after the muffler and how much water will
run back upon shutdown."
This is a nifty design.
Just Right Marine
figured it out. And Tallahassee Welding and Machine Shop created the
Being able to utilize a
tractor motor in a boat means I'm saving money. The quirks
to marinize her do add to the final tab. Of course, I'm still way ahead of the
$14,000 price tag for a new Yanmar 18hp diesel marine engine even with the
complications. That's $14,000 plus installation!
Photo updated 21 May 2015.
coolant (green) side required a water tank. The water
and antifreeze will circulate through a heat exchanger aka external
water tank. It's a closed
system* and will eliminate the difficulties that can occur when raw
water runs through a motor.
*Closed system: The same fluid flows through and
returns to the tank aka heat exchanger. There is no overboard discharge for this
portion of the cooling system.
Here is a picture of my oversized black heat exchanger
and the stainless manifold:
That heat exchanger is far larger than
necessary for my little Kubota from
Yanmar Tractor Parts.
It was free and therefore is perfect. This coming week it will be bolted
to the forward bulkhead in my engine room.
Hoses will be attached and soon, really
soon, my Seaweed should be mobile. I am excited and look forward to
swimming off the boat in green water again. I have missed that.
Life is good afloat. And progress is being made.
I am entirely grateful
for the feedback regarding my cooling system. THANK YOU does not even
begin to express my sincere appreciation for the education. J.
PLEASE NOTE: I posted links to this article on
several sites and received feedback. Below are some pertinent points to
consider should you opt to power your boat with a tractor motor. My
responses are in italics.
Update 21 May 2015. Please bear in mind these comments were prior to the
updated pictures. Originally I had the flow of water backwards. That is fixed
now. Also the entrance of the raw water was just after to top elbow. The
water enters exhaust pipe just prior to pipe extension on the far right. A
hose attaches to that pipe, and from there the raw water and hot air flows
to the water lift muffler and out.
With apologies. I am woman, and having
been married can attest to making mistakes. For proof positive of that,
contact my former husband.
Comment from DougR on
CruisersForum: Your project looks
like a lot of fun. As you mention, repowering a trawler with a
tractor engine isn't for everyone, and there are lots of
things which must be considered. Seeing as you threw the
project out there, I thought I might make a few comments that
might save some grief down the road.
The piece of stainless
steel art that you refer to as an exhaust manifold might more
properly be called an exhaust elbow or riser. From the photos,
I see that it is probably designed to bolt onto the factory
dry manifold at the two bolt flange. What I can't see are any
other brackets to provide additional support. This is a rather
long heavy part to support only with the two bolt flange, and
when it gets full of water it will be even heavier. Without
substantial additional support it will almost surely crack or
cause the dry manifold to crack.
You're correct DougR,
and yes a mounting system for the stainless manifold, or
riser, is in the works. Even empty, it's a heavy piece.
As I understand your
drawings, the freshwater coolant will enter close to the
exhaust pipe entrance, and exit on the bottom on the other end
of the unit. The problem I see here is that there will be a
large amount of air trapped at the top of the rise, with no
way to purge the air out. This air will cause expansion
problems within the freshwater coolant system. I suggest you
add a bleeder valve at the highest point of the water jacket
to get rid of the air when the system is filled.
I'll take that up with the mechanic tomorrow. Thanks.
This system will probably
last for many years, but welded stainless exhaust systems in
contact with salt water have a history of pitting in and
around the welds. When pitting occurs the engine coolant will
disappear out the exhaust without a trace.
I think the heat
exchanger you have chosen will have enough heat rejection
capacity for the engine, as well as the heat that will come
from the exhaust elbow, but just be sure the plumbing on the
freshwater side of the system is as direct as can be, and has
low pressure drop. You want to be sure the circulation pump
has the ability to push an adequate volume of water.
Good luck with the project DougR.
And the following day Doug wrote: I did a
bit more thinking about the bleeder valve, and while I think
it is necessary to bleed air from this high spot, I think I
would do it slightly differently.
As you might know, engines frequently manage
to put "air" into their freshwater cooling systems. This can
come from minute compression leaks, suction leaks at the circ
pump seal, etc. and most engines have some sort of bleed
system to get this air out of the engine and into the
expansion tank. It is not unusual to see bleed hoses running
from high spots on the engine, such as turbochargers, after
coolers, etc. to the expansion tank on the top of the heat
In the case of a tractor
engine like yours, the normal path this air would take is up
the top radiator hose and into the expansion area at the top
of the radiator. Because you will have a built in air trap in
the riser I would suggest a small hose fitting on the high
spot and a hose that runs to another fitting in the expansion
tank section of your heat exchanger.
This will constantly
bleed a little bit of coolant and any trapped air out of the
system. The hose can be as small as 1/4 inch, but it needs to
have a constant rise from the engine to the expansion tank to
avoid an air lock.
TrawlerForum offered this: 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.
That's why everyone else
makes the "mixer" removable/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.
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.
Eric on Willy (Willard
Nomad 30) from
TrawlerForum said: 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 flexible
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 would be
just 4 90 degree elbows and longer vertical pipes.
I personally like the water
jacket idea and perhaps a "V" shaped strut (or pair of same)
could be fabricated 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?
My reply: The exhaust
manifold is copper.
As for supporting that
stainless riser/manifold, in addition to the two bolts at the
engine, another bracket was mocked up that will support the
middle portion of the unit. Next to me is a welder (steel
shrimp boat) so he will torch cut the metal needed.
The stainless will be
mounted to the engine so it will move in synch with the motor.
Hoses will run between the heat exchanger and the unit, adding
And thanks for your
advice and input. This is all new to me so having outside eyes
is more helpful than you can imagine. Thank you Sir.
Another fellow from
TrawlerForum states: 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
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 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.
More from Eric
on M/V Willy:
Here is my riser setup. Built by
National Marine Exhaust in Marysville, WA for $750 in 2005.
All SS and not water jacketed ... just water injected.
The green hose carries the spent seawater to the
near top of the riser (fairly high) and the "T" at the bottom of
the green hose is for water injection to the PSS shaft seal.
The riser is mounted w 4 studs on the exhaust
manifold. One of the studs can be seen and they are further
apart that it looks. Re Vibration and mechanical security the
outlet rubber hose to the lift muffler is quite stiff and my
plastic (Poly Flex) engine mounts don't allow much engine
movement even at idle. But not much engine vibration is felt on
I've never seen underneath the heat shield
blanket so don't even really know what it looks like but it's
very effective shielding the engine compartment and stray human
parts from getting burned on the exhaust parts. The insulation
on that red wire is completely intact and not damaged by the
I was in Alaska when this was installed on Willy.
I had no input re the design short of telling MM Exhaust about
my boat. Everything was what they thought it should be. Don't
know how I could improve on it after almost 10 years and 800 hrs
of use. I had fairly constant trouble w the cast iron that was
on my Yanmar (previous boat) and sought out a more trouble free
riser. The typical cast iron risers are fine but require
replacement close to once a year. They don't take much trouble
to replace and clearly are the cheapest riser solution. Things
get more complicated as the riser is built higher.
So I submit the standard hardware usually
employed for this mission is simple, direct, economical and
effective. Any variations takes one into the world of
experimentation. A place I'm fairly comfortable in to an extent
few here would follow my trail.
As I've said I kinda like your "riser/manifold"
but re what some of the other more conservative guys have said
there is definitely room for troublesome events or
"miss-functions". Loosing your coolant or even catching fire
probably won't happen and if anything resembling that happens
you have good experience and seamanship to deal w whatever.
Eric continues: At this
point I see two very big problems. My suggestion of cross
mounting and "V" struts will require very stout hardware and
excellent mounting points. Success? Probably but maybe not. The
other problem is metal expansion and contraction. The outside of
the box will always be relatively cool but the internal pipes
and 45s will be very much hotter. The box will want to grow in
all directions but the pipe will grow lengthwise much more so.
It will want to bust out at one end. Also the cool water
injection pipe will be attached to the outer mass of metal (box)
and the internal heavy and very hot pipe. Makes me wonder if
there are any other weldments inside attaching the internal pipe
to the outer box. If so there will be a great tug-o-war going on
between the box and internal pipe. If not a lot of forces will
be acting on the one thing holding (or trying to hold) the
internal water injection pipe to the box.
Janice, Doug R's input seems
very good to me. Read it again and see if anything comes to
The subject of this article and more details on
decisions, options and choices when transforming a tractor motor
into an engine suitable for a boat are found in the next article.
It is online now, and I solicit your opinions on this process.
The new article is:
Project Second Opinions
Is there anyone else who has put a tractor engine in a
Are there any specific surprises I should be looking for, besides great
Regarding the Comments Section,
found at the end of every article:
Before you type in each block be
sure to hit the backspace key. Coding inserts a space in every box.
Your email address will come back as malformed unless you remove
that space. (You don't have to include your email address.)
The capcha is case sensitive.
© 2015, 2023
In the Bilges,
Antique Speedboat (ID sought) ~
Previous Post ... ... Next Post
Project Second Opinions