A boat motor from a power tiller with his hands


A series of articles about homemade “all-terrain” PLMs was published in “M-K” 0 12 for 2018. As the author, I presented the magazines with these materials to my colleague Aleksey Ovchinnikov, and he extracted from the storerooms of his garage the “leg” of a 4-hp American Evinrude 4506A motor with an oblique “bog-walker” gearbox as a return present. So I, of course, had a strong desire to try the “novelty” in practice

It was very interesting to delve into the history of this design. In 1952 the American corporation OMC, which produced boat engines under the Evinrude and Johnson brands, began selling a new 3-horsepower Evinrude/ Johnson “Lightwin” submersible motor. It only had a displacement of 86 cm3. But it was two-cylinder, what provided excellent equilibrium and stable work, both at maximum and minimum rpm. Weight of the “engine” was also very small for its capacity of 30 pounds, that is only 13.6 kg. These two features are reflected in its name, loosely translated as “the lightweight couple”. But there was one more “zest” of Lightwine which distinguished it from all competitors. It could be equipped with a special “swamp” bevel gear. The gear housing and anti-cavitation plate were narrow and tapered, allowing them to pass freely through thickets of aquatic vegetation. “The gear spur had a small “ski” underneath, so that the outboard could literally “drag” along the bottom at low speed. The two- or three-blade propeller, with saber-shaped blades that did not wind grass around it, also contributed to this feature.

boat, motor, power, tiller, hands

The emphasis in the advertising for the Johnson “Sea-Horse 3” motor from ONS (1952) is precisely on its “swamping” capabilities. Three drawings demonstrate operation of bevel gear in grass and shallow water

“Lightwin” was produced from 1952 to 1967 in three generations, differing mainly in appearance. However, in the third version there was another unique novelty. a folding “leg”, similar to the one that was later used in the Soviet “Sputnik. And from 1967 until the end of the existence of OMC produced a more forced, but essentially the same motor with power increased to 4 hp.с. Its gearbox had not undergone any changes at all for all that time. My “Evinrud” was made, as the nameplate says, in 1974, at the European branch in Bruges.

After receiving such a royal present from my friend, the first thing I did was to disassemble the gearbox to examine its performance, to pour in fresh oil and to remove the water pump, which was not needed for the air-cooled motor I was going to install. The design of the gearbox was very unusual and very simple at the same time. There are no roller bearings: the shafts are only 11mm in diameter and rotate in long bronze sleeves, and the propeller shaft sleeve can easily be removed along with the lip seal. Usually a gearbox of a boat motor has a pinion shaft which is connected to a vertical shaft by a splined or other connection. There is no pinion shaft as such here. The vertical motor shaft fits directly into the gearbox sleeve and the bronze pinion sits directly on its splines.

In spite of the small motor power the bevel gears have circular teeth, which ensures silent operation of the gearbox.

Gear ratio 17:28 (≈ 0.61). Curiously, a similar design with shafts on slide bearings had a Soviet PLM “Priboy”, the creators of which, as you know, were inspired by the 5-horsepower “Johnson”.

“Leg” of motor with gearbox removed and adapter plate installed, made of Teflon-coated aluminum pan. Notch on left for oil sump drain plug Transition plate. the gaps in the square coupling tool head to compensate for the inevitable misalignment of the shaft options of design transitional coupling: a) using the tool head, b) threaded Way to install the “marsh” propeller with landing thread M18x2, 5 on the propeller shaft diameter 11 mm “marsh” propellers left rotation: top-steel domestic American type, bottom-Thai of the aluminum alloy. The seat threads of the screws are the same M18x2,5

As a motor head “hybrid” was supposed to use a four-stroke “vertical” single-cylinder air-cooled Lifan 1P64FV with a working volume of 135 cm 3 and a capacity of about 5 liters.с. Previously, this engine stood on the Naro-Fominsk machine-building plant produced a small series of PLM “Nara-4,7”. In fact, it was the same “hybrid” on the “leg” from the “Salyut-4” (see the “hybrid” on the “leg”). “M-K”-2018). The only difference between my engine and the factory version was that the carburetor air and throttle valves are unlocked and operated independently. Variants of the transition plates of hybrid motors with similar “lawnmower” engines are shown by me in the past publications (see. “M-K” 8 for 2018). This time in my storeroom I couldn’t find scraps of dural, so, following the example of many other “hybrid builders”, I made a transition plate from an aluminum frying pan, matching the diameter and color. Although, it is worth noting that due to much greater strength and hardness, dural D16 is still preferable to “kitchen aluminum”.

The transition socket from the engine crankshaft shank to the vertical shaft of the PLM was made with a long “10” tool head. For this I had to cut off the top end of the vertical shaft with splines and make a hexagon on it. The head was warmed up on the shaft to provide an interference fit. The play required for compensation of possible shaft misalignment remains in the upper part of the tool head. Details of the design of the adapter coupling are shown in the drawing. The tool head is the weakest link in the torque chain, so it is always wise to have a spare one with you.

Evinrud-Lifan hybrid with a Thai-type propeller ready for bench tests

The transition “crankshaft ICE vertical shaft PLM” can be made even easier if you cut the splined end of the vertical shaft, cut an inch thread on it and screw the shaft directly into the internal thread of the crankshaft. However I like this variant less because of peculiarities of Evinrude gearbox construction, when the driving gear “sits” directly on the vertical shaft. Then all vibrations caused by the misalignment of the shafts will be transmitted to the hubs and gears of the gearbox.

The steering is of the “Salut” type, but with a more convenient sliding tiller and with a “stop” button at the handle end. For tilting the engine there is a bracket-handle, made from the step of “Salyut” power tiller.

Unfortunately, the gearbox I got in my hands did not have a propeller. Such “Evinruds” were equipped with a two-blade “swamp” left-hand rotation propeller with a diameter of 6% inch (158.75 mm) and pitch of 6 inches (152 mm), or a three-blade propeller of the same diameter with pitch of 5½ inches (140 mm). If you can afford it, you can order one from the USA. But this is not our method In Russia you can find other similar screws, and much cheaper.

First, these are Thai-made aluminum propellers from the SPS company for “long-tail swampers” like “Longtail” (see “Longtail”). “M-K” 1-2018). Diameter of a propeller for the motor capacity of 6-9 liters.с. is 614 inches (165 mm). Pitch is unknown and can not be measured precisely because of the very high concavity of the blade profile. The weight of the propeller is only 100 grams. Overall, this product has a good quality casting and is very reminiscent of a propeller from an old Soviet Strela motor (see. “M-K”.2018).

Design by Yuri from Petrozavodsk: engine Honda GCV160, adapter plate made of track disk, screw. “native” Evinrude

Secondly, these are stainless steel screws for American Go-Divil type PLMs. The price for them is absolutely inhuman, but near Moscow company “Methodius” has established the casting of similar propellers for motors of 6-9 and 15 22 liters.с. for quite reasonable money. The first one is 7 inches (178 mm) in diameter and 5 inches (127 mm) pitch. The weight of the steel propeller is of course much higher than the aluminum one, and amounts to 530g. The manufacturer claims domestic 12X18H10T stainless steel is stronger than American steel. I must say, however, that I liked the quality of casting less than I did with the Thais. The screw is very unbalanced and needs to be reworked with a file.

Both “swamp” propellers Thai and Russian-American are designed for threaded fitting (thread diameter 18 mm, pitch 2.5 mm). The design of the adapter to install the propeller on 11 mm diameter propeller shaft is shown on the drawing. The transition sleeve is made of a drilled along stainless bolt M18x65 with a cut off head.

The dry mass of the resulting American-Chinese Evinrude-Lifan hybrid made 17,5 kg with a steel propeller and 17,0 kg with an aluminum one, that is not bad at all for a four-stroke 5 hp outboard. From the Internet I know only one similar design on exactly the same “leg” from Evinrude. As a motor head on it is installed engine Honda GCV160 working volume of 160 cm 3 and capacity of 5.5 hp.с. The author, Yuri from Petrozavodsk, used not a traditional frying pan as a billet for the transition plate, but a track and field disc for throwing. The transition socket is made simpler than mine, with a thread on the vertical shaft. The propeller is used “native” Evinrude. It should be noted that “Honda” is noticeably lighter than “Lifan” of similar power, so Yuri’s engine is even lighter. only 13 kg.

The tests of the swamp buggy were conducted in the Tver region on a small forest river Chervonka, a tributary of the Volga Medveditsa. And the cross-country capability of this design in an overgrown pond exceeded all my expectations! I had to literally “iron” bushes of water lilies for half an hour before the first blade of grass got wound around the propeller.

The famous Evinrude bevel gear with a steel “bog” propeller installed Another “swim” through a field of lilies The Chervonka River is a tributary of the Volga Medveditsa. On such small overgrown reservoirs the compact and light “swampwalker” is indispensable!

The speed of a catamaran with a gross weight of about 300 kg (load of two people) on open water was about 10 km/h with a steel propeller from “Methodius” and 12 km/h with a Thai aluminum propeller (measurements were made by GPS navigator). That’s about what I would expect: saber-shaped “swamp-propelled” steel propellers usually have lower efficiency than universal aluminum propellers, but they are much stronger and more durable.

I will have to reconsider the results of comparative tests of “all-terrain” PMs, given in the previous article (see. “M-K” 2-2018). It can be stated that the motor with an oblique “swampwalker” gear almost in no way inferior to the normal one, but has a significantly higher cross-country in shallow and overgrown reservoirs, claiming first place in this rating.

Only one thing is not clear to me: why nowadays they don’t make PLM with such reducer as well as with folding “leg”, because “Evinrude” brand still exists? However, now it belongs not to the American company OMC, but to the Canadian concern BRP (Bombardier Recreational Products). Perhaps some patent restrictions prevent this, or maybe it’s just that the entire old Evinrude/Johnson motor line is buried by the new owners and forgotten

How to properly use a boat motor from a brushcutter?

Using a grass trimmer as a boat motor, the operator needs to constantly monitor the condition of the engine, and give it time to cool down.

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In addition, to extend the life of the boat motor from a grass trimmer will help:

  • Checking all the fasteners available in the device. before each start of the motor, you need to carefully inspect the fasteners that hold the elements of the engine from the grass trimmer;
  • filling the engine from the grass trimmer only with the gasoline and oil that was used to operate the brushcutter;
  • timely cleaning and replacement of the engine air and fuel filter;
  • regular inspection and timely replacement of the fuel pump;
  • Inspection and, if necessary, replacement of the spark plug.

Prolong the life of the boat engine from a grass trimmer will also help to regularly ventilate its regular cylinder. To do this about once every 2 months you need to unscrew the spark plug, and 4-5 times rarely pull the starter rope. After the procedure, the plug can be screwed back into place and the engine can continue to run.

What you need to know before you make a boat motor from a chainsaw?

Contrary to the majority opinion about the futility of this venture, experienced mate-experts are unanimous: the boat motors of modern chainsaws work on a par with their original counterparts. Of course, this will require time and effort, as well as certain consumables, chief among which is the gasoline saw itself. But given the fact that the motor equipment boat will cost a lot of money, self-made gasoline saw becomes the only chance to equip your floatation with a motorized traction and no more paddling with oars.

As a pulling basis is better to take professional high-powered chainsaws made in Europe, such as “STIHL” or “Husqvarna”. But the owners of domestic brands should not be upset either: saw motors “TAIGA”, “Ural” or “Druzhba” with a skilful approach can be adapted to this kind of self-made.


Consider the construction of transport on low-pressure tires. Need a frame, left over from an old motorcycle, which is welded to an already self-made frame. The motor is mostly taken new, to avoid breakages at the most inopportune moment.

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The motorcycle engine of “Tula” type is the best choice. The ignition is best suited from a tractor, a conventional battery is not worth relying on. Then we install the fuel tank, fix the rudder and the seat.

The front fork of the Ural type without shock absorbers is just right, then a chain drive is installed. This design is often done without brakes, to stop it is enough to stop the engine. Wheels are easier to take from a combine harvester, with the upper layer of rubber removed.

Boat motor from an electric screwdriver

Screwdrivers are best suited for making motors for the boat. You should choose a device for operating voltage of 12 V, so you can install a battery from the car, the capacity of 45-55 amp-hours. The device is refined elementary.

Lifting mechanism

The task of the lifting mechanism is to move the motor in different planes, both horizontal and vertical in order not only to operate the watercraft, but also to be able to lift the motor out of the water. The simplest construction is a system of clamps, which is used to attach the electric screwdriver to the lifting mechanism. The lifting mechanism should be rigidly attached to the boat, especially if the boat is rubber. There should be rings on the clamps, through which the tube passes, and inside the tube passes a shaft made of a steel rod of suitable diameter. To make it slide easily, bearings are installed inside the tube.

Gear and propeller

An electric screwdriver develops a lot of speed, but for a homemade electric motor for a boat, you do not need it, so you need a reducer. The gearbox from an angle grinder is the most suitable option. To fix the gearbox, the upper part of its shaft is simply clamped in the chuck of an electric screwdriver.

You also need a propeller, it’s better to make it of stainless steel, 2,5-3,0 mm thick. You should not use aluminum or plastic.

  • First of all, a square billet is cut out, measuring 30×30 cm.
  • In the center of the workpiece is marked a square of 5×5 cm and diagonal lines are drawn through the corners. Along these lines it is necessary to cut the workpiece to a small square.
  • The 4 petals are rounded and rotated to an angle of 30 degrees.
  • In the center of the product you need to drill a hole for mounting on the gear.
  • After that, the propeller is installed in its place and securely fastened.

Boat electric motor with their own hands

At one time, when King Hammoori still lived, he argued that time spent fishing was not included in the accounting of the total time of life. This is stated by many citizens who like to spend part of their free time fishing.

As a rule, most anglers own a boat. Many boats, especially modern ones, are equipped with gasoline engines. And a boat without a motor, especially if you have to fish in the water expanses of a large lake becomes a burden, which requires a huge expense, effort and energy to move. And here you definitely need a motor: gasoline or electric. makes no difference.

And yet, special attention should be paid to the electric motor, because:

  • Electric ones do not require oil or gasoline for their work, which means that there are no exhaust fumes, which is not harmful to nature;
  • electric motors are smaller in size, weigh less and do not take up much space. This is especially true if you have to fish far away, and every kilogram of extra weight is always felt;
  • they are much more cost-effective than their gasoline counterparts;
  • modern designs are assembled on modern parts, developed by modern technologies, so at a minimum weight have maximum power.

But these statements take place if the owner of the boat already has an electric motor and has felt such benefits in full. What to do if you don’t have one?? So, you need to make it yourself.

homemade boat motors (continued from /2018)

In the previous article we considered the lightest “hybrid” boat motors, made on the basis of the Soviet “Salyut” with trimmer motor heads. Their weight and dimensions make them beyond competition, but they have a number of serious drawbacks, such as high noise level, high fuel consumption for their power, unstable operation at low rpm.


The four-stroke engines with vertical shaft, the so-called “lawnmowers” are devoid of the above disadvantages. Therefore, if you read on the Internet people’s experience, it becomes clear why they are most often attracted to self-made mowers, who especially like about half the fuel consumption of the classic two-stroke engines of the same power.

Most four-stroke “lawnmower” engines, as well as trimmers, have a similar design one air-cooled cylinder with the impeller on the flywheel, lubrication of moving parts by splashing oil poured into the crankcase, gas distribution mechanism with the boom valve drive (the so-called OHV scheme), single-type simple carburetors with a float chamber, simple and reliable electronic ignition system with a fixed ignition advance angle, throttle control through a centrifugal speed regulator designed for a maximum 3,600 rpm.

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

The American Briggs and Stratton engines have a special place among “lawn-mowers”, but now they are produced anywhere but in the USA. Many of them have an extremely archaic lower-valve timing scheme, abandoned by automakers in the 1940s. However, for low-speed motors such scheme has a right to exist, because it provides a “dense” layout and, accordingly, small dimensions.

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

Most companies do not publish the external speed data of their products, except for the most serious manufacturers: in Japan it is Honda, in China Zongshen. For example, let’s look at diagrams of dependence of power and torque on revolutions for Zongshen XR-140A motor. You can see that this characteristic is opposite to the one typical for two-stroke trimmers reviewed in the previous article. “Lawnmower” motors “do not like” high revolutions. To accelerate them above 4,000 rpm is useless, since it does not increase power, and the service life decreases catastrophically.

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

External speed characteristic of the motor Zongshen XR-140A with a working volume of 140 cm 3

As already mentioned, all Chinese “lawnmower” motors have much in common, which they inherited from Honda. In particular, the diameter of the circumference, which is located fixing holes in all engines with a working volume of 100 to 225 cm3 is the same 203.2 mm, that is 8 inches. However, the angular placement of the holes may be different and does not lend itself to any logical explanation. Truly, “the East is a thin business,” and the marking of the adapter plate each time should be carried out individually. As an example, the Champion motor mounting holes are shown. There are five apertures on the drawing but in reality there are from three to four on the engine.

The greatest variety of “design schools” among self makers is observed in the matter of making transition couplings. Vertical shafts of Chinese “lawnmower” motors are unified. Almost all are 22.2mm (7/8) or 25.4mm (exactly 1in) diameter with a keyway groove. On the shaft axis is a blind threaded hole, unfortunately, for very rare at us inch threads 3/8-24UNF-2B or 7/16-24UNF-2B. Recently, the Chinese have finally started to gradually switch to metric threads M10x1 (Zongshen NP100) or M8x1,25 (Champion G170-1VK). There are several options for making “in the garage” adapter couplings with respect to the vertical shaft of the motor “Salut.

Most common among homebuilders uses a “on 22” tool head. It is desirable that it has such a cross section as shown in the drawing: in this case it mates well with an ordinary key. The main disadvantage of such a scheme is the inability to provide a tight connection with minimum clearances. Accordingly, the key inevitably breaks. It has to be made of mild steel, otherwise the shaft keyway will break, which is much worse. I used a similar connection in one of my designs. After a season of operation, the key had changed from rectangular to trapezoidal, so it should be considered a consumable item, just like a propeller pin.

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

The third way seems to me the best. It is suggested that the crankshaft end be ground to a square cross-section that matches the size of the tooling adapter. For the 22″ shaft.The 2 mm is 1/2″ (12.7 mm) square and for a 25.4 mm shaft is 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 undertook this job the first time, my hands were a little shaky for fear of damaging the new motor. But now I’ve already done this operation three times, not counting the grinding of vertical shafts, and I can say that it’s really not difficult to grind a round shaft shank to a square cross-section. Of course, if you do it manually, the accuracy will be about ±0.2 mm. Therefore, to make the fit tight, it should be done “hot”, with heating of the encompassing part (adapter) to 150 200° C.

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The main characteristics of four-stroke engines with vertical shaft

Another feature of four-stroke engines for agricultural purposes, which deserves a separate consideration, must recognize their control. They are all designed to run at a constant speed of 3,000-3,600 rpm, regardless of load.

A mechanical centrifugal regulator is used to maintain rpm. When you increase the load rpm drops, and the regulator opens the throttle of the carburetor, when reducing the opposite. That is why it is impossible to overtorque the engine with the centrifugal regulator, when the load is removed, the regulator will immediately turn the throttle to idle position. Correspondingly, they are always started with the throttle fully open.

Joint transition coupling with keyed connection Joint transition coupling with threaded connection (Zongshen NP100) Joint transition coupling with grinded crankshaft end to the square 12,712,7 mm Diagram of fixing holes on Champion engines (bottom view)

Obviously, for a boat motor for which there is no danger of sudden load shedding (unless the propeller is lost), this is unnecessarily complicated. That’s why most selfmade engineers, including me, remake this scheme for direct throttle control, which allows stable operation of the engine at a low throttle (without auto-oscillation) and slightly exceeds the maximum speed of 4000 rpm and, accordingly, the power. Of course, in this case there is a danger of “overclocking” the engine, but it is interesting that it warns about dangerous conditions. At high revs the valves start to knock noticeably, because the valve springs do not have time to close them. If to persist and run in this mode for more than a few minutes, oil through the ajar valves gets into the combustion chamber. The engine starts to smoke with black smoke and abruptly revs down or hangs up.

Diagram of throttle control of a carburetor with a centrifugal regulator Diagram of direct throttle control of a carburetor without a centrifugal regulator

In the summer of 2014, after returning from my first vacation with the boat, I realized that 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. “I sold the Honda, put the light but very noisy trimmer Sputnik in half and put it in the home museum for now, and turned my thoughts to more powerful and less noisy four-stroke engines.

I figured out that the engine had to be: light enough (not more than 15 kg, to be not heavy, and the main thing not to roll over our less than 3 meters long boat, like the Vetorok did), powerful enough (not less than 4-5 liters) to try to put it on the gyre.с., to try to bring her to the plane, at least with a minimum load) and four-stroke, air-cooled it was my initial acquaintance with the two-horsepower Honda.

And such a motor I met in a store on Budyonny Avenue (the location of the aircraft engine plant “Salut” is no longer a state secret). It was called “Nara-4,7” and was a Chinese “lawnmower” air-cooled motor Lifan 1P64FV with 135 cm3 volume and 5 L.с., installed on the “leg” of the good old “Salut” with an enlarged three-blade propeller. The weight of the whole construction was exactly 15 kg.

The first question I asked the salesman was the following: “Isn’t the gearbox of the Salyut too weak for a five-horsepower motor head??” I heard back: “It’s not a Salut gearbox, it’s a reinforced one, although it’s in the same case.”. It seemed to be true, as a closer inspection showed that its propeller shaft was made of harder steel, and the propeller pin had a diameter of 4 mm, not 3 mm, like on the “Salut”. I think they used a gearbox and propeller of a never yet put into production four hp “Salyut”. Also I, of course, inquired about the reliability of the unit and whether it is possible to buy it at all? The seller confidently stated: “In five years we sold as many as 50 units (!) And so far none has been returned to us!”Well, that’s a noble risk

So, I became the owner of the first and only new motor in my life “from the store”, with the factory number 005. General impression: good, very light, designed by aviation engineers, and not the cheapest copy of the Chinese Honda, combined in one construction, on the level of the Jaeger club. It didn’t start well, it kicked my hands with backfires, the tiller of “Salut” is very weak for five powers. But if it was “started”, it worked well. The boat with a total weight of 150 kg accelerated to 15 km/h, which corresponds to Froude’s displacement number of about two, that is almost planing. Fuel consumption was about 1l/h. The motor is very quiet and stable at idle, which is very important for trolling.

The most interesting element of Nara’s design is the transition plate. A large number of mounting holes ø8.5 drilled by me, as it was consecutively mounted Lifan 1P64FV, Champion G140VK and Zongshen NP100. Though the plate was made of “winged metal”, we could see that its designer didn’t worry much about making it lighter.

“Nara-4,7”, original factory version of 2010 with Lifan 1P64FV engine

The “Nara” adapter coupling 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 immediately remade the tiller, 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, uncontrollable ignition advance, and here, to make them work at uncharacteristic lawnmower higher revolutions, the ignition is made too early.

Now our homebuilders have learned to use electronic ignition with a variable advance angle for similar engines, but then, in the fall of 2014, Chinese “lawnmower” motors of the new generation, significantly lighter, were on sale. Their crank mechanism design already had a decompressor to eliminate the flashback problem. In those happy years the question cost made not more than 4000 So I decided not to suffer with the morally outdated “Lifan” and to put the new Champion G140VK on “Nara. With about the same working volume of 140 cm3 and about the same power, the complete motor was lightened to 13.5 kg and no starting problems. I hope to say that I couldn’t find an inch strip for 3/8″ thread, so I made a coupling with a key.

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

Another problem of the Nara was the propeller. As I said before it has an excellent three-blade propeller A.В. Barinova BAV-11, originally designed for “Salyut-4”. Its diameter is 184 mm and pitch is 110 mm. But it was designed for the engine with rotation speed of 5000 rpm, but it does not suit at all for the low-speed engine with rotation speed of 3600 rpm! It was necessary to develop either a new gearbox with lower gear ratio or a new propeller with increased pitch. As a result, the engine “twists” already at about two-thirds of the throttle, and it is impossible to keep the engine at 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

The main characteristics of hybrid outboard motors with air-cooled four-stroke engines

The above is illustrated by the presented diagram of external and screw characteristics, built by the approximate methodology described in the previous article. It is seen that with the BAV-11 the speed of the four-stroke engine with a working volume of 135-140 cm3 is much higher than the allowable 4000 rpm. You need a more hydrodynamically “heavy” left-hand rotation propeller. I had such after experimenting with trimmer motors. This is a plastic screw from Chinese motor Troll 2.5 190 mm diameter (7/4), pitch 102 mm (4) and a screw from a defunct American Johnson 3R four-horsepower engine.190 mm diameter (71/2), pitch 152 mm (6). If the first of them differs from the “Barinov” only by worse workmanship, the “Johnson” turned out to be very successful. In addition, well proven itself a two-blade propeller from the “Moscow-10” with pitch 242 mm, turned to a diameter of 185 mm.

Diagram of external and screw characteristics of “hybrid” boat motors on the basis of PLM “Salut” with four-stroke air-cooled 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 a very low fuel consumption, which is important in remote areas, such as in Karelia, where gas stations are still only available in the district centers. At the end of the 2016 season, the weakness of the Salyut’s four-power stern tube still became apparent. The catamaran got a little jammed between the two mooring bridges. Instead of culturally releasing it, I turned the motor to reverse and gave full throttle, which resulted in the “leg” breaking in half.

After his return to Moscow motor was restored, but the fall of that year the sale were extremely primitive and cheap lawn mowers, which were the latest innovation of Chinese motor industry as lightweight “engine” Zongshen new series NP. The weight of the NP100 with a working volume of 99 cm3 and a power of 2.5-3.0 liters.с. was only 6.8 kg. For the first time the Chinese have mounted on it a gas tank made of transparent plastic, which is very convenient for a boat motor. When mounted on the same “Nara” mass assembly was only 12.3 kg. And as you can see from the chart, optimal for this motor head is exactly the “native” propeller for “Nara” BAB-11.

Oka, autumn 2014, the author on the running tests of “lawnmowers

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

Would it be possible to recommend this modification to all owners of old and defective “Salutes? From the point of view of the final result, of course, yes! You get a great trolling motor, light, compact, and capable of hours of almost silent operation at low revs with minimal fuel consumption. But there is a big problem with the propellers. OEM ones are categorically unsuitable for “Salut”, because a four-stroke engine cannot develop even half of its power with them. All suitable left-hand rotation propellers. “Barinovsky” BAV-11, from motors Troll, Johnson, “trimmed” propeller from Moskva-10, long ago taken out of production, are rather rare.

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Control of the engine and other constructional variants

Although the electric motor is ready, it is not yet capable of making turns. In order not to turn by means of the paddles, small modifications should be made to the design. It is enough to attach a bolt to the central part of the mount, on which you then put a tube. This makes it possible to make turns by changing the position of the base and, therefore, the electric motor.

You can weld another handle to the base, with a regulator on it, which is responsible for supplying current to the motor. It is reasonable to use a rheostat. But in this case you will have to modify the drill itself, connecting the motor, located in its body, with the rheostat. This creates a more functional design.

an electric screwdriver as a motor

There are several ways you can make an electric motor. An electric screwdriver can be used instead of a drill. By design it almost does not differ from the device with a drill. The distinguishing feature of the product is the lower cost of its maintenance. So, one twelve-volt battery will be enough for six hours of operation of the device. However, you will have to sacrifice speed because of the lower power.

To make the watercraft move faster, you can use propellers with a larger pitch. In addition, as in the previous case, an electric motor based on an electric screwdriver can be equipped with handles, which facilitate steering.

Electric motor from trimmer

A trimmer will also work fine for this purpose. The process of creating a motor using this device will be greatly facilitated. The only thing the craftsman will have to do is to shorten the length of the device and attach a screw to it. There is no need to mount a gearbox.

There is also no need to modify the control and the system responsible for powering the motor. The only difficulty that may be encountered along the way is the problem of attaching the device to the boat. Particularly for the inflatable. But it is solvable.

As an electric motor, you can use units, at the expense of which windshield washers work, or a simple electric motor. In the latter case there can be difficulties with the power supply because the standard motors work on an AC voltage of two hundred and twenty volts. The problem can be solved by installing an inverter.

Thus, the owner of a watercraft can create an electric motor for a boat with his own hands. This does not require any special skills. It is only necessary to purchase the necessary materials and prepare some tools. As a motor, it is recommended to use a drill of more than one hundred and fifty watts. Such an indicator will allow the boat to move both in standing water and on the river. In addition to the drill, you can use a trimmer or a regular electric motor. Another option is an electric motor based on an electric screwdriver. Such device is cheaper in maintenance, but there may be problems with the speed of movement of the floating device.

The need to convert an ordinary boat into a motorboat may arise for a variety of reasons. But here’s how to do it, if the budget is limited and there is not enough money to buy a ready-made motor. There are many options that help to make a quite working boat motor from improvised materials, which are available in every home.

Features of a homemade engine

When converting a motor, it is worth considering that they were developed to perform different functions. Grass trimmer operates at high revolutions and a small torque, and the boat motor must do the opposite. Therefore, remaking the device requires special tools and even a drawing.

Engine from a trimmer for grass to construct is more convenient and easier, since it has a number of necessary component mechanisms:

  • a very economical engine;
  • Built-in unpainted fuel tank, allowing you to easily control the amount of fuel;
  • the presence of a starter and gas in the device;
  • a boom equipped with a rigid shaft.

It remains only to buy the missing parts or make them yourself and you can proceed to the manufacture of the engine for the boat.

The grass trimmer operates at high revolutions and low torque, while the boat motor should do the opposite

What can be made

There are several possible options for modifying the grass trimmer for a motor for a floating vehicle.

A very simple way, but requires additional financial expenses.

It will be necessary to purchase such parts:

  • Clamp for attaching the device to the transom of the boat.
  • Propeller. You can buy a ready-made set over the Internet, since stores may not have such products. Included is a special drive, made of stainless steel, as well as universal adapters for flexible shaft trimmer for the grass, which allows not to bother with the fact that they fit to your model or not lawnmower.

Sometimes a clamp may be included, so before you buy it clarify what is included in the kit.

The drawing of the attachment to the trimmer is shown in the manual. For installation will take about half an hour.

For the conversion you need an angle gearbox from an angle grinder, a screw, which can be cut from a sheet of stainless steel, as well as gaskets and bearings for the fasteners. This method allows you to get the maximum speed, despite the small pitch of the screw. In the field, the device requires additional adjustment, which is done using pliers.

This method is performed as much as possible with your own hands. Let’s consider it in more detail on the example of a lawnmower with a two-stroke motor with a capacity of 25 cm 3. Weight of 4.5 kg and power of 700 W is equipped with a bent leg. Grass trimmer with such power allows the boat to move at a speed of about 5-7 km / h. For modification we will need an angle reducer from an angle grinder, a propeller, which can be cut from a sheet of stainless steel, as well as seals and bearings for fasteners

What will be needed

To make it, you will need materials, as well as tools:

  • Grass trimmer.
  • Duralumin with a thickness of 2 mm. It is needed for the propeller.
  • Screw clamps or any other device for attaching the device to the boat.
  • Welding machine.
  • Fixing elements.
  • Additional tools for the job.

All necessary elements can be bought or made by yourself. A blueprint may be needed to design a homemade propeller, but not for the drive. The size of the propeller depends directly on the power of the drive, as well as the weight of the watercraft. For example, a propeller with dimensions of 10×3 cm is able to move a vehicle weighing about 120 kg.

Instructions for making

To make a boat engine from an ordinary grass trimmer you will need to do the following steps:

For the running-in of the homemade engine you will need a tank of gasoline (0.5 liters).) with oil in the ratio of 1:40. One tank of fuel covers about 10 km of ground. The speed of the watercraft with such a motor is in the range of 5,6. 7,9 km / h depending on the loading of the boat.

  • It is much easier to retrofit a grass trimmer with a straight shaft.If the rod has a curved shape, it will need to be completely replaced, because the steel cable will not be able to transmit the necessary torque. To modify the bent shaft you will need to use a duralumin tube, press a sleeve of bronze into it and mount it in an appropriately fitted holder.
  • The screw should be made according to the drawing in duralumin.Its dimensions can always be adjusted if required.
  • The screw should be installed in place of the trimmer head.Be sure to make a ring nozzle to protect the cylinders.
  • You can order ready-made kits online and save time creating the elements yourself.All necessary shaft adapters and drive unit are included, sometimes even a clamp is included.
  • The device can be operated using the starter handle, but very often it is inconvenient to use.It can be easily replaced with a normal bicycle gear shift.
  • A screw clamp is used to mount the motor and it is attached to the boat transom.

The presence of an engine on the boat greatly facilitates the life of its owner. However, gasoline engines make a lot of noise and consume a lot of resources. The alternative to this kind of motive power. electric motors. These are quiet units that run on cheap electricity and are slightly inferior to gasoline boat engines in efficiency. This version of the engine will cost less, the more so, it is possible to make an electric motor on a boat with your own hands.

In the name “electric motor” lies the essence of the device, which it denotes. An electric motor for boats means a unit that drives the watercraft through the movement of the blades. Its action is based on physical laws. The peculiarity of electric motors is the resource they consume to perform their functions.

Today, fuel-powered boat motors are widespread all over the world. An electric motor for a boat, unlike similar units, works by consuming electricity rather than gasoline. Among some boat owners there is a widespread opinion about the low efficiency of such devices. But it is wrong. If properly designed, the electric motor is able to provide enough thrust force to move the watercraft on the water at normal speed.

In addition, a homemade motor has a number of advantages, for example:

  • The final cost of building such a device will be much lower than the market value of factory gasoline engines and electric motors.
  • Current environmental laws in the country strictly regulate the use of electric motors for boats. These rules do not apply to homemade units.
  • The device works with little or no noise. This feature will be especially useful to fishermen, because any loud noises can scare away potential catches.
  • Electricity is cheaper than fuel materials. In addition, devices equipped with internal combustion engines consume incomparably more resources than homemade electric motors.
  • The owner of the boat has the opportunity to choose the appropriate power of the unit for him independently. The basis of the homemade motor is a drill or other devices. It is their power that determines the characteristics of the future engine. Whichever device the craftsman chooses, this is the performance of the electric motor.

To create a homemade electric motor is fairly simple. It is enough to follow the instructions clearly. But will need certain materials and tools. There should be no problems with access to them. Most of the necessary tools are already in stock for any owner. All materials can be found on sale in retail outlets. It is not difficult to find the drawings required for the work.

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