View Full Version : Marinizing Small Industrial Diesels

Diesel Dan
09-23-2004, 11:15 AM
There are a number of Kubota and Yanmar industrial diesel engines available in the sub-50 HP range that would be great to marinize, but for one problem: availability of water-cooled exhaust manifolds. Anybody know of a source?

09-25-2004, 06:48 AM
Sorry about the delay,

Is the site for Marine Exhaust of Alabama .

1-251-928-1234 in USA ,

They have a very complete catalog of exhaust manifolds and some other conversion equippment.



03-16-2005, 04:54 PM
Hello All,
I have a kubota 1505 diesel taken from a commercial mower. It has less than twenty hours on it. I'm toying
with the idea of using it in a small houseboat. Probably something like a narrowboat for river use. NO more than five to ten knots max.

What is about the minimum required of this engine for marinization? I understand at this point (I'm just beginning this learning curve) that considerations involve fresh/salt use, heat, noise, compartment space, auxilliary uses, and legal requirements. I guess the ideal set up would be to build a 12kw genset around it and use electric propulsion. I could use the AC for aux uses. But it appears that affordable small craft electric propulsion is a few years off yet from what I'm able to learn on the internet. Hydraulics sound appealing as well, esp for adapting auxilliary stuff -but potentially messy and less efficient than mechanical drives.

Could you comment on just a few options I might consider?
Thank you for any help you can provide.
Brad Williamson

03-18-2005, 05:11 PM
By the time you end up buying a transmission, bellhousing,adjusting the timing, adjusting the pump and other things, it should be cheaper to get a used marine engine. However, if you are looking for a project to kill time, get the specifications for a marine engine, including the camshaft, and compare them with what you got.

03-26-2005, 04:00 AM
Briggs and Stratton has an electric motor (ETEK), that
has been used in everything from robots to dirt bikes for
years! I'm surprised that no one has converted it for marine
use, as it's nearest competitor (solomon tech) costs nearly
20 times as much, for the same horsepower. They only
cost around 400US$ !
I was wondering about them, as well as marinizing the Briggs
23HP freshwater diesel engine. I don't know what to do about
a transmission for it tho... :?:

James :idea:

03-26-2005, 05:02 AM
The simplest is belt drive , although reverse is a problem.

Better but more $$$ is a simple hyd drive, which is complex , but gives a power source for anchor retreval or other toys.

Full throttle FWD to REV in a second or two with NO harm.

There is NO reason to have a water cooled exhaust , when doing it as a dry stack is far cheaper and more reliable.

A proper INSULATED (heat & noise) engine box with an air blower is needed , some engineering but little co$t.


03-26-2005, 11:05 AM
Hydraulics are more expensive than a mechanical transmission. Also, the power loss will be 25-35% compared to 3%. You should add that to the cost. It will mean a bigger engine with a higher fuel consumption for the same useable HP.

03-26-2005, 04:09 PM
"Seems to me that a really ideal setup would have a 12k generator on my kubota charging an electric lift-truck battery (two to three grand, very compact, extremely long lived, and efficient). I'd get a bow thruster/primary drive unit similar to the following...." No Way, Have you even seen a boat before. You can find marine diesels for next to nothing that need rings and a valve job all over the place. You don't want some Rube Goldberg contraption in your boat. Go to a salt water toun and serch all of the marine diesel shops and pick one up.

03-27-2005, 03:11 PM
Try ZF marine transmission. They carry/have small transmission by the name Hurt

03-27-2005, 07:54 PM
ZF Hurth and Kansaki Hurth.A old german gear box company that sold out

03-28-2005, 04:12 AM
ZF bought Hurth and is now called ZF HURTH MARINE S.p.a. in Italy.

They have ZF4M, ZF5M, and ZF10M for the 16 to 41 Hp. range. Web site I remember they have Hurth Marine gear as low as 8.5 Hp.

HangZhou Advance Gearbox Group Ltd. of china has marine gearbox for 12.5 Hp and 33Hp. coded 06 and 16A. E mail

To marinize a water cooled diesel engine you will need a heat exchanger. Either keel cooled or intercooler.

01-03-2007, 04:16 PM
EC Power Systems in WA, OR, ID CO, & UT have developed a marine engine w/ Orca Marine Cooling Systems for the Kubota D905, D1005 & D1105 engines and are working on developing other systems to marinize Kubota engines for the Pacific Nortwest marine market. Call Craig @ 206-436-6060 or e-mail @ for a flyer and purchase options.

02-07-2007, 03:11 AM
Hi Craig.

A very good industrial engine which is successfully marinized is the Isuzu.

Models 4JB1 and the 4EL1 .

Here is the spec for the 4JB1 :

The Engine
Isuzu Model 4JB1 OD Exhaust elbow outlet 2.5 or 3
Aspiration Natural OD Raw water inlet 1
Cylinders Four OD Fuel Inlet 10mm
Bore x Stroke (mm) 93 x 102 OD Fuel Return 10mm
Displacement (cc) 2771 Alternator AC 12 volt 94 amp
Engine Rotation Counterclockwise, viewed from flywheel
Maximum Engine Output kW (hp) 50 (67) @ 3000rpm
Maximum Torque 181 Nm @ 2000rpm
Approx.Fuel Consumption @ 1500rpm: 75% Load 4.6 litres/hour
(note that fuel consumption will vary substantially with load and rpm)
The Transmission
ZF Model ZF25
Single speed , vertical offset, direct mount
Maximum rated input 107kW (143hp). Pleasure duty.
Reverse reduction integral marine transmission, with hydraulically actuated multi disc clutches.
Available Ratios 1.969, 2.80

Professionally marinized $7500 US
If you want, email me and I will send you details etc of the company. (my only connection is that I am replacing my 80hp Ford Lehman with the Isuzu , which puts out better HP at 1750 RPM.

sal's Dad
02-07-2007, 02:27 PM
As noted, one problem with the small diesels is finding an appropriate transmission. As near as I can tell, the lowest (highest?) reduction Hurth/ZF makes on its little gearbox is 3:2. I got one on ebay, approx 1.9:1, but it is gonna be sloooowww.

I need more like 5:4 for my "Rescue Minor". (I briefly considered a direct drive, using extreme rudder angle for reverse) Any thoughts?
Sal's Dad

David H
02-22-2007, 06:58 PM
Hey .....any chance ya still got that slloooow tranny cause it would be the perfect speed for me. Let me know if its for sale. Cheers, David

02-23-2007, 04:29 AM
"Rescue Minor"

Is this an Alden,New Jersey Sea Bright skiff?


sal's Dad
02-23-2007, 04:56 AM
Rescue Minor is a 1940's Billy Atkin design - 20'x6'x6", designed for 15-20 mph on 20hp.

The hull is evolved from the "Sea Bright skiffs" of the New Jersey beaches, with a wide flat keel, with the prop projecting from the aft end, completely protected by the keel. Atkin took this a step further, so the entire after underbody is a tunnel, the prop half out of the water at rest.

If/when I find a better transmission, I'll put the 1.9:1 up for sale.
Sal's Dad

02-24-2007, 04:05 AM
Atkin seemed to stop at 20 -25ft or so.

Do you know of any design that has this bottom in 35ft or so?

A look in the Power boats section will point to a thread.


sal's Dad
02-24-2007, 06:10 AM
There are at least two Atkin Tunnel Sterns in the 35' range: River Belle, and one which is not in the catalogue, but was built a few years ago by Alex Hadden (see his advertisement in MAIB).

Dave Gerr has designed larger, heavier, and slower tunnel stern cruisers; a few are featured on his website. Also, take a look at Carlson's Alligator .
Sal's Dad

Claus Riepe
02-24-2007, 10:20 AM
Sorry to interrupt.

With regards to the initial subject of this thread:

I have a 9.5 hp aircooled industrial Kubota in one boat. It is a petrol engine, but the following observations would apply also for the range of small Kubota Diesels.:
It is a complete success. Inexpensive, quiet, incredibly lightweight. No marinization was needed in my case. The exhaust piping is flanged directly onto the silencer/exhaust of the engine. The exhaust piping is done from copper heating pipes, 1 1/2" resp. 1". The exhaust is dry, i.e. uncooled.
The system is in an open boat on salt water. Sure, the mild steel parts do rust a good bit since day 1, but ever sincethe engine itself is sound, works without fail or any renewed parts for four years now. Engine comes complete with tank, electric starter, small charger coil. Engine is a robust commodity used mostly for generators. Costs new around US$ 700.00, available almost anywhere. Very simple to install too.

The PTO is on the camshaft of the engine, so it is already 2:1 reduced.
Directly attached, i.e without any -reversing- gearbox, is a variable pitch propellor system, which in addition allows the propellor blades to be flattenend into a 'sail' position, no drag.

The complete system engine+shaft+propellor weighs around 30kgs, with the centre of gravity is almost midships and very low in the hull.

OK, they rust, but what the heck, the main rusting parts, the mild steel silencer and exhaust parts can be replaced for very little money and with little effort.

Hope this helps.

sal's Dad
02-24-2007, 10:46 AM
"It is a petrol engine...
... No marinization was needed in my case"

I would be very concerned about the fire hazard in a petrol (that's gasoline, right?) installation you describe.

There have been a number of discussions and warnings here about the danger of using non-marine fuel and electrical systems in a boat. In an auto, or generator, any fuel spills ar dissipated relatively harmlessley on the ground. In a boat, spills and fumes stay in close proximity to the electrical system, and sparks.

Please be careful!

"Sorry to interrupt..."
No problem ( I'm rarely offended by a return to the original topic ;-)

Sal's Dad

Claus Riepe
02-24-2007, 01:18 PM
"It is a petrol engine...
... No marinization was needed in my case"

I would be very concerned about the fire hazard in a petrol (that's gasoline, right?) installation you describe.

As I said, it is an open boat. All the ventilation one may like or dislike, all the time. The boat was originally equipped with a gasoline inboard engine too. Never any probs. Boat is over 30 years now.

Anyway, I am not at all advocating industrial gasoline engines instead of industrial Diesel engines, I just wanted to point out that it is surprisingly little fuss to put small industrial engines into boats. There is also a range of suitable aircooled small industrial Kubota Diesels and I could have taken one of those as well, except they are heavier, bigger, noisier and more expensive.

Industrial engines can work on boats.


08-23-2007, 01:07 PM
You can skip the gearbox alltogether, and use a direct drive, with a Kitchen Rudder". This is a clamshell type rudder, that opens and closes, to vary the speed, and allow reverse, and even a neutral of sorts. They are amazing devices to operate, and work perfectly. I have been aboard a boat with one of these rudders, and it was amazing, wide open forward to wide open reverse without touching the trottle! They are alttile hard to build, but not real expensive. Do a internet search, for kitchen rudder, and you can see a couple of different examples. With this rudder, a dry stack exhaust, and an electric cooling water pump, you would not need any marinization to your engine, other than a heat exchanger, if you wanted freshwater cooling.!

09-15-2007, 11:08 AM
Don't know about availability in the US, but in Europa there are Chinese diesels on the market. Exact copies of a Honda 10 HP, but somewhat cheaper. I bought mine thru Ebay a couple of years ago and paid the equivalent of $ 400 for a brand new engine (electric starter) in a frame and with an attached waterpump that I threw away. I use it to power a 5 KV generator.

Claus Riepe
09-15-2007, 03:43 PM
We had been looking at the chinese Diesels, and could have got them for an even lower price than you indicated, if we would have gotten together an order for 10 pcs. .
However, in the end we resisted, for two reasons.
We could not get information on the technical specs of the camshaft PTO, how much axial force onto it would be OK.
Secondly, such Diesels require a much more sophisticated engine foundation in the boat than their petrol peers, with rubber shock absorbing elements, flexible elements in the exhaust line, and flexible coupling elements between engine and driveshaft.
On the other side, petrol engines run so smooth they can be bolted directly onto a sturdy marine plywood foundation, not requiring shock absorbers anywhere.

Anyway, I am sure there are today chinese engines available that would fit the requirements without probs, only we were early adopters and were still a bit cautious.

09-16-2007, 01:23 AM
Secondly, such Diesels require a much more sophisticated engine foundation in the boat than their petrol peers, with rubber shock absorbing elements, flexible elements in the exhaust line, and flexible coupling elements between engine and driveshaft.C.

The Chinese have a different view on vibration: they simply screw the engine on a tube frame without any rubber parts at all and let the thin walled tubes absorb the energy.
The engine itself behaves like any other 1-cyl. diesel, Honda, Ruggerini, Kubota, Hatz etc. If you see and hear it running at 3000 rpm you can't believe it has any life expectancy at all....

09-16-2007, 06:24 AM
..snip.. If you see and hear it running at 3000 rpm you can't believe it has any life expectancy at all....

Here in China, boats (like the one in my sig, above) putt-putt past here at about 1000 to 1500 RPM I'd guess. They're obviously dry exhaust. Some even have mufflers... There are 40+ of them in the harbor here and I look them over every day when they come back in. I've yet to see any repairs, (or even any maintenance). But my Mandarin isn't good enough to ask any questions, yet!

More photos at

Here's a nice engine I'm thinking of using:
and I do have the advantage of being able to get one at the factory, I think...

09-16-2007, 09:31 AM
Being that close to the source, you are much better informed than I am.
I have no clue as to who manufactures these small diesels. Mine came with a decall from the Austrian company that wanted to trade diesel powered water pumps, ordered some containers full and than discovered the market wasn't large enough so they used Ebay to dump them.
In the plastic bag with 2 wrenches, a sxcrewdriver and a bottle of oil there was a tiny piece of (rice?)paper with a poorly printed Chinese-english messages that if I ever needed any spares I could order them for the Honda so-and-so. No name, no nameplate on the engine.
I took the liberty of changing the oil after 25 hours, but while doing so I noticed it was almost as clean as when it went in. Sometimes I try to be original, but some habits are deeply rooted.
Your 3 cyl. watercooled machine looks quit sophisticated. Does it resemble a model from Yanmar or is it really designed from scratch?

09-16-2007, 06:42 PM
The Photo of the engine looked like it had 4 injector pipes from the pump -
the spec said 3 cyl. ???

09-16-2007, 08:16 PM
The Photo of the engine looked like it had 4 injector pipes from the pump - the spec said 3 cyl. ???
Yes, their website uses the same photo for all the engine models...

09-17-2007, 01:26 AM

Thanks for the photographs. I took a look at Shekou on Google Earth. Big place! Where are you berthed? :D

Please post more views.



09-17-2007, 02:42 AM
TerryKing,Thanks for the photographs. I took a look at Shekou on Google Earth. Big place! ..snip..
Hi Pericles, let me try this.. Hmmm.. That didn't work... (A .kmz file = Google Earth location) is not allowed. OK. QRX..
--------------(fooling around)----------------
OK, there is an attachment with the FAKE name of do NOT UNZIP it, just rename it to Shekou-China.kmz. Click on it (if you have GoogleEarth) and it should fly you to a view of the fishing port area.

Photos: See
(There is a Boats album there). I want to create an album and start a thread here about WHAT the different types of boats are, their construction and how they are used in the fishing business... TBD.

08-12-2009, 03:59 PM
if you took the engin of of an industrial lawnmower there should be some good
peices you could use of of it such as the radiator and drive asembly you dont state the make of the lawnmower :?:

View Full Version : Marinizing Small Industrial Diesels