Boat motor from a power tiller with his own hands

Other devices used to create a boat motor

Ways to create a motor actually exists quite a lot, most importantly, the right approach to the process of selecting related parts and the most suitable base. In addition to an electric screwdriver you can make use of a power tiller or trimmer for grass. But the best technical characteristics will have a boat motor from a chainsaw with their own hands.

Due to the fact that the fuel consumption in this kind of motor is minimal, it is often made from this device. At the same time the tank will have a clear view. Homemade propeller, which acts as a propeller, is often made of duralumin. The edges must be carefully sharpened and the propeller blades must have a 10mm bend. The ring attachment, which is necessarily used to make such a motor, is designed to protect the boat from damage during operation.

Use adapters to connect the propeller and motor shaft together. It is necessary to take the starter motor out of the lawnmower. Using the pre-prepared drawing, you can proceed to create a motor from such an element as a trimmer for grass.

The motor can also be constructed from the starter, taken from such a device as a single-axle tractor. To assemble a four-stroke model, use a fuel system of the usual type, but make sure that excellent quality indicators were exactly at the pump, designed to pump water. If there is any old engine, you can remove the so-called deadwood.

Over the carburettor you have to mount the fuel pump in such a way that it doesn’t have the slightest contact with the rocker arm. Locking bars may be used to secure it in place. Crankshaft should be mounted directly above the pinion at the top. The water pump should be installed under the stern tube. Use springs to keep the lower piston free to operate.

A rack for the motor with their own hands

To save money a rack for a boat motor with their own hands, is created on the basis of not needed product with wheels. This will allow you to make your own adjustments during production and harmoniously fit the part into the overall design.

This product helps to safely store the motor in winter or during service. Thanks to the reliable fixation it is much easier to organize the reconstruction or to carry out an oil change, lubricate the screw.

In addition, it facilitates starting the engine and performing other work related to product servicing. It is worth paying attention to increase safety during transportation.

The model from the power tiller

To assemble homemade boat motors from a power tiller is quite difficult, but it is possible. If we consider electric modifications, then first of all the starter is removed from the device. In addition, it is necessary to disconnect the engine. If a four-stroke modification is used, then the fuel system will fit the most common. The water pump in this case it is important to choose a quality. In turn, the deadwood can be taken from an outdated boat motor. To fix the fuel pump, many use different fixators. The easiest way is to mount it over the carburetor. At the same time, it should not come into contact with the rocker.

The crankshaft on boat motors (homemade) should be placed over the upper gear. At this stage it is necessary to check the strength of the clamp. The sump, in turn, should not overlap it. The water pump in this case is installed under the stern. In order not to interfere with the work of the lower rod, many experts advise the use of special springs. After fixing them, you will only need to fix the screws and tiller.

Boat motor from a chainsaw. How to make with your own hands

In order for the chainsaw to turn into a boat motor, you need to attach a special attachment. Thanks to the device with a three-blade propeller and gear with a ratio of 2:1 you will be able to develop speed on the boat up to 20 km / h, with a minimum fuel consumption of 1 liter per hour.

A chain saw boat motor

The principle itself of creating a homemade from a chainsaw is to use the saw equipment as a kind of drive. With the right device and the availability of schemes, you can make many devices on the chainsaw engine. You will make a boat motor with the help of a special attachment with blades.

The fact that chainsaws are characterized by great engine power, small size and weight, allows you to apply the power unit in many areas of activity and under any environmental conditions. The boat motor, which was assembled on the basis of a chainsaw, has a special tightness, which allows the user to apply it in any position.

Prefabricated nozzle set

Now they sell special attachments for converting grass trimmer into a boat motor. Such an attachment includes everything necessary for attaching it to the gasoline mower motor. The control handle and the switch button are mounted on the boom. Gas handle is made with the ability to switch speeds and equipped with a ratchet that secures the desired position.

The kit includes a fixture for mounting the unit on the boat. Grass trimmer attachment can be assembled easily, it has a simple design. To reassemble, attach throttle cable to the motor and then secure the muffler cable. The nozzle costs in a specialized store about 5 thousand. rubles.

Boat motor with his own hands from a trimmer for grass

A great homemade boat motor is obtained from the trimmer for grass. Such an electric motor is made simply because of the similarity of the devices.

There is no need to take something away from the grass trimmer or power mower and greatly remodel it. In particular, the upper gearbox remains the same, as well as the engine power and control system.

How to Make a Homemade Boat Motor for Under 90.

The option is considered very profitable and convenient, because the device has a transmission and an engine. It remains to make a mount for the watercraft, remove the area with the disk and put a propeller. But let’s not forget about the disadvantages.

  • It is worth remembering that the motor for the boat from a grass trimmer has low power. It is difficult to swim against the current of such a device.
  • Boat motor from a grass trimmer is ideal for moving on small bodies of water with standing water. And this is not always the limit of dreams of fans of outdoor activities.
  • You will have to get used to the strong noise effect and smoke.

In general, such a homemade boat motor turns out to be not quite a cheap option because of the cost of the brushcutter. But if you already have one and it is defective, you can easily convert it into a propulsion system for a variety of floatation models. It is suitable for small boats, it will hold a boat made of plywood because of the lightness of construction and inflatable too.

Recommended reading: How to choose an outboard boat motors?


Blueprints of a swamp buggy often involve an additional trailer. If there is a need to transport goods, you can make a cart to it.

You’ll need tractor wheels or wheels from a power tiller. Mounting is suitable for the simplest, for example, a through pin with a lock. Such a design will help to move the load on loose or wet soil in places with no road connections.

Homemade from a power tiller: what and how you can make?

Such a variety of small tractors as a single-axle tractor is a universal means of small-scale mechanization, which facilitates its owner to solve most issues related to the care of the land plot. Rich set of attachments allows to significantly expand the functionality of such machines.

Another advantage obtained by the owners of power tillers, the creation of new machines on their basis. Let’s take a look at what can be made out of a powerboat, and how.

homemade lawn mowers (Continued from /2018)

In the previous article we considered the lightest “hybrid” boat motors, based on the Soviet “Salyut” with trimmer motor heads. According to their dimensional and weight characteristics they are beyond competition, but have a number of serious drawbacks, such as high noise, high for its capacity fuel consumption, unstable operation at low speeds.


The above mentioned disadvantages are deprived by four-stroke motors with vertical shaft, so called “lawnmowers”. That’s why if you look on the Internet with people’s experience it becomes clear why they mostly attract self-made engines, which especially like approximately twice less fuel consumption than the classic two-stroke engines of the same power.

The majority of four-stroke “lawn-mower” engines, as well as trimmer ones, have a similar design: one air-cooled cylinder with a propeller on the flywheel, moving parts lubrication by splashing oil into the crankcase, and timing mechanism with a boom valve train (the so-called OHV circuit), Single-type simple carburetors with float chamber, simple and reliable electronic ignition system with fixed ignition advance angle, throttle control via centrifugal speed regulator designed for maximum 3,600 rpm.

Many engines have a decompressor, a simple mechanism that slightly opens the exhaust valve at low rpm and thereby greatly facilitates starting. In general, we can say that all Chinese engines of this type roughly reproduce similar in parameters “Honda” of the previous generation.

boat, motor, power, tiller, hands

A special place among “lawn-mowers” is occupied by engines of the American company Briggs and Stratton, though produced now anywhere, but not in the U.S. Many of them have an extremely archaic lower-valve timing scheme, which car makers abandoned back in the 1940s. However, for low-speed motors, such a scheme has the right to exist, since it provides a “denser” layout and, accordingly, small dimensions.

On the contrary, the engines of Japanese Honda and Robin-Subaru are distinguished by the high-tech layout with a camshaft in the cylinder head (the so-called ONS scheme), respectively, they can be “cranked up” to a frequency of over 4000 rpm. But the price of “Japanese” is approximately three times higher than that of “Chinese”, they are also twice as expensive as similar in parameters Briggs and Stratton motors.

Most companies do not publish the external speed data of their products with the exception of the most serious manufacturers: Honda in Japan and Zongshen in China. Let’s look at the diagrams of Zongshen XR-140A engine power and torque vs. revs as an example. You can see that this characteristic is the direct opposite of that typical for two-stroke trimmer motors, considered in the previous article. “Lawnmower” motors “do not like” high rpm. To accelerate them above 4,000 rpm is useless, because the power is not increased, and the service life is reduced catastrophically.

As always, when assembling a “hybrid” PLM the homebuilder faces two main tasks: making the transition plate between the deadwood and the engine seating plane and the transition coupling between the engine crankshaft and the vertical shaft of the “leg”.

External speed characteristic of the motor Zongshen XR-140A with a working volume of 140 cm3

As already mentioned, all Chinese “lawnmower” motors have a lot in common, which they inherited from Honda. In particular, the diameter of the circumference, on which the mounting holes are located, in all engines with a working volume of 100 to 225 cm3 is the same 203.2 mm, that is 8 inches. True, the angular placement of holes may be different and can not be explained by any logical explanation. Truly, “East is a thin business,” and the marking of the adapter plate needs to be done individually each time. As an example, the holes for the installation of Champion engines are shown. The drawing shows five holes, but in reality there are from three to four holes on the motor.

The greatest variety of “design schools” among homebuilders is observed in the matter of making transition sockets. The vertical shafts of Chinese “lawnmower” motors are unified. Almost all are 22.2 mm (7/8) or 25.4 mm (1″ exactly) in diameter with a keyway. There’s a blind threaded hole in the shaft axis, unfortunately, for the very rare 3/8-24UNF-2B or 7/16-24UNF-2B inch threads. Recently the Chinese have finally started to switch to metric threads M10x1 (Zongshen NP100) or M8x1,25 (Champion G170-1VK). There are some variants of making “in garage conditions” of transitional couplings with reference to the vertical shaft of motor “Salut”.

The most widespread among selfmade people is using the tool head “on 22”. It is desirable that it has the cross section as shown in the drawing: in this case it mates well with the usual key. The main drawback of such a scheme is the impossibility of ensuring a tight connection with minimum clearances. Accordingly, the key inevitably breaks. Thus it should be made of a soft steel, differently the keyway of a shaft will be broken that is much worse. I used a similar connection in one of my designs. After a season of operation the key section had changed from rectangular to trapezoidal, so it should be considered as consumable, like a propeller pin.

An alternative version of the adapter uses a threaded hole in the crankshaft. The main problem is finding a die with an inch thread, not a pipe thread, but a machine tool thread.

The third way seems to me to be the best way. It is suggested to grind the end of the crankshaft to a square section corresponding to a suitable sized tool adapter. For a 22 diameter shaft.2 mm is 1/2″ (12.7 mm) square, and for a 25.4 mm shaft, 3/4″ (19 mm) square. Turns out, it’s not hard to make four perpendicular flats, even with a simple “angle grinder” with a sanding disc, without disassembling the motor. When I took on this job the first time, my hands were a little shaky for fear of ruining the new motor. But now I’ve done this operation three times, not counting the grinding of vertical shafts, and I can say that it’s really not hard to grind a round shaft shank to a square cross-section. Of course, if you do it by hand, the accuracy will be about ±0.2 mm. Therefore, to make the fit tight, it should be done “hot”, with the heating of the covering part (adapter) to 150 200 ° C.

Highlights of Vertical Shaft Four-Stroke Engines

Another feature of agricultural four-stroke engines that deserves a separate consideration is their control. They are all designed to run at a constant speed of 3000-3600 rpm, regardless of load.

A mechanical centrifugal regulator is used to maintain rpm. RPMs drop with increasing load and the regulator opens the carburetor throttle, and vice versa with decreasing load. It is therefore impossible to “overclock” an engine with a centrifugal regulator, and when the load is off the regulator will immediately turn the throttle to the idle position. Accordingly, they are always started with the throttle fully open.

Transition coupling with keyed connection Transition coupling with threaded connection (Zongshen NP100) Transition coupling with grinded crankshaft end on square 12,712,7 mm Scheme of fixing holes on Champion engines (bottom view)

This is obviously unnecessarily difficult for a boat motor that is not in danger of suddenly losing load (unless you lose the propeller). That’s why most self-made engineers, including me, change this scheme for direct throttle control, which allows stable work of the engine at a low gas (without oscillations) and slightly exceeds maximal speed of 4000 rpm and correspondingly the power. Of course, in this case there is a danger to “overcorrect” the motor, but it is interesting that it warns about dangerous modes. At higher rpm the valves start to knock noticeably because the valve springs do not have time to close them. If you persist and run in this mode for longer than a few minutes, oil will enter the combustion chamber through the ajar valves. The engine starts to puff up with black smoke and sharply revs down or shuts down on its own.

Diagram of carburetor throttle control using centrifugal regulator Diagram of direct throttle control of carburetor without using centrifugal regulator

In the summer of 2014, after returning from my first vacation with the boat, I realized that the Honda BF2 is an excellent and reliable motor, but I will not go under it again, because it is not interesting to test the Japanese equipment. “Honda” sold, light, but very noisy trimmer “Sputnik” folded in half and put it in the home museum, and my thoughts turned to more powerful and less noisy four-stroke engines.

I figured out that the engine has to be: light enough (not more than 15 kg, not to be overpowering, and the main thing is not to roll over our boat, which is less than three meters long, like Vetorok did), powerful enough (not less than 4-5 liters), powerful enough (not less than 4-5 liters), strong enough to keep the engine in good condition and keep it in good working condition.с., to try to get her on the plane, at least with a minimum load) and four-stroke, air-cooled here affected my initial acquaintance with the two-horsepower Honda.

And such motor I met in a store on Budyonny avenue (a location of air-engine plant “Salute” already not the state secret). It was called “Nara-4,7” and was a Chinese “lawn-mower” air-cooled motor Lifan 1P64FV with the volume of 135 cm3 and a claimed power of 5 liters.с., mounted on the “leg” of the good old Salyut with an enlarged three-blade propeller. The weight of the whole construction was just 15 kg.

The first question I asked the salesman was: “Isn’t the gearbox of the Salyut a little weak for a five-horsepower motor head??” The answer I heard was: “It’s not a Salyut gearbox, but a reinforced one, albeit in the same housing”. It looks like truth, because closer acquaintance with it showed that its propeller shaft was made of harder steel, and the propeller pin had a diameter of 4mm, not 3mm, like on the Salut, but 4mm, like on the Veterek. I think they used a gearbox and propeller of the never-launched four-horsepower “Salyut” in this design. Also I, of course, inquired about the reliability of the unit and whether I could buy it at all? The salesman said confidently: “In five years we have sold as many as 50 units!) and up to now none has been returned to us!”Well, the risk is a noble thing

So, I got my first and only new motor “from the store”, with serial number 005. General impression: a good, very light, designed by aviation engineers “Salyut” leg and not the most trashy Chinese copy of Honda combined into one construction at the level of the circle of young technicians. It didn’t start well, and it would hit my hands with backfires, and the tiller arm of the Salyut was very weak for five powers. But if it started up, it worked well. A boat with the total mass of 150 kg accelerated up to 15 km/h, which corresponds to the displacement number of Froude about two, ie almost planing. Fuel consumption is about 1 liter per hour. The motor is very quiet and stable at idle, which is very important for trolling.

The most interesting for us element of the design of “Nara” adapter plate. A lot of ø8.5 holes were drilled by me, because I’ve mounted consecutively Lifan 1P64FV, Champion G140VK and Zongshen NP100 on it. Although the plate is made of “winged metal”, you can see that its designer didn’t care much about making it lighter.

“Nara-4.7”, original factory version of 2010 with Lifan 1P64FV engine

Transition coupling “Nara” is made according to the scheme with a threaded insert. Apparently, it wasn’t much of a problem for the aircraft factory to find a strip with an inch thread.

I changed the tiller at once, put a sliding, large diameter, but it was more difficult to cope with the problem of starting. “Lawnmower engines have a constant and, most importantly, unregulated ignition advance, and here, to make them run at uncharacteristic lawnmower elevated rpm, make the ignition too early.

Now our homebuilders have learned to use electronic ignition with a variable advance angle for such engines, but then, in the fall of 2014, Chinese “lawnmower” motors of the new generation, significantly lighter, were on sale. Their crank mechanism was already equipped with a decompressor to eliminate the flashback problem. In those happy years the price of the question was no more than 4000 That’s why I decided not to suffer with the morally outdated Lifan and put the new Champion G140VK on the Nara. With about the same working volume of 140 cm3 and about the same power the motor assembly became lighter to 13,5 kg and there were no problems with starting. I hope to tell you that I couldn’t find one-inch bit for 3/8″ thread, so I made the coupling with the key.

Another drawback of the “Nara”, confirming its haste in creation is that they forgot to equip it with a handle for folding and carrying. For a hybrid, this is an absolutely essential element. The air-cooled motor heated up to over 100 ° C simply has nothing to grasp. After getting a few burns, I first attached a wooden door handle, rather crudely made. Later installed a stylish plastic “duck” in its place, designed for winding mooring ends. A pleasant surprise was that when you turned the motor 180 degrees, this handle rested against the clamp and prevented the motor from tilting, allowing the boat to back up.

Another problem with the Nara was the propeller. As I said before, it has an excellent three-blade propeller A on its own.В. Barinov BAV-11, originally designed for “Salyut-4. Its diameter is 184 mm and pitch is 110 mm. But it was designed for a 5000 rpm motor and is totally unsuitable for a low speed 3600 rpm motor! We had to develop either a new gearbox with a smaller ratio or a new screw with a larger pitch. the engine starts to overtorque already at about 2/3 of throttle and cannot be turned on full throttle for a long time.

“Nara-4,7″, sea trials on the Oka, speed” 15 km/h Drawing of the adapter plate of the boat motor “Nara-4,7” “Nara” with the Champion G140VK engine on the transom of the catamaran

Main characteristics of hybrid outboard with air-cooled four-stroke engines

This is illustrated by the presented diagram of external and screw characteristics, built according to the approximate methodology described in the previous article. It can be seen that with BAV-11 the speed of four-stroke engine with working volume of 135-140 cm3 is much higher than allowed 4000 rpm. The more hydrodynamically “heavy” propeller of the left rotation is necessary. I had these after experimenting with trimmer motors. This is a plastic screw from Chinese motor Troll 2.5 diameter 190 mm (7/4), pitch 102 mm (4) and the screw from the discontinued fourhp American motor Johnson 3R.Diameter 190 mm (71/2), spacing 152 mm (6). If the first of them differs from the “Barinov” only by the worse quality of workmanship, the “Johnson” was very successful. Besides, a two-blade propeller from the Moskva-10 with the pitch of 242 mm turned to the diameter of 185 mm has proved itself well.

Diagram of external and screw characteristics of the “hybrid” boat motors based on PLM “Salut” with air-cooled four-stroke engines

After all the upgrades this motor turned out to be the most versatile of my designs. In the summers of 2015 and 2016, it was pulling not only a light boat, but also a 300-kilogram two-seater catamaran at up to 12 km/h, while maintaining very low fuel consumption, which is important in remote areas, such as in Karelia, where gas stations are still only available in district centers. At the end of the 2016 season, however, the weakness of the Salut stern tube for four powers became apparent. Catamaran slightly wedged between two mooring bridges. Instead of culturally releasing it, I turned the motor to reverse and gave full throttle, causing the “leg” to break in half.

After returning to Moscow, the motor was restored, but in the autumn of that year the sale were extremely primitive and cheap mowers, which were the latest innovation of Chinese motor industry as much lightweight “engine” Zongshen new series NP. Weight of the NP100 with a working volume of 99 cm3 and power of 2.5-3.0 liters.с. was only 6.8 kg. For the first time the Chinese have mounted on it the gas tank of transparent plastic, which is very convenient for a boat motor. When mounted on the same “Nara” assembly weight was only 12.3 kg. Thus, as it is visible from the diagram, optimum for this motorhead is exactly “native” for “Nara” propeller BAB-11.

Oka, autumn 2014, the author on the “lawnmower” running tests

Short sea trials of “Nara” with Zongshen NP100 engine took place on Oka river in August of the last year. The engine gave an impression of being optimal for our 40 kg boat. Speed was 10-12 km/h depending on load. But the Zongshen started worse than the previous Champion G140VK. I think the lightweight flywheel is to blame for this, since in low-powered “lawnmower” motors its function is partially taken over by the lawnmower blade. In order to improve starting properties, the throttle control was converted to a centrifugal-controlled circuit. Now the engine “starts” with a fully open throttle and the regulator puts it in its place.

Would it be possible to recommend such modification to all owners of old and faulty “Salutes? In terms of the end result, absolutely, yes! You will get an excellent trolling motor, light, compact, and capable of almost silent operation for hours at low RPM with minimum fuel consumption. But there is a big problem with the screws. Regular ones are categorically unsuitable for “Salut”, the four-stroke engine cannot develop even half of its power with them. All suitable left-hand drive propellers. “Barinov” BAV-11, from Troll, Johnson engines, “trimmed” screw from Moskva-10 that was taken out of production long ago. are rather rare.