How to make a boat motor from a grass trimmer

Methods for making a boat motor from a grass trimmer

There are three ways to make your outboard motor from a grass trimmer. They differ from each other in the parts used and the principle of self-assembly.


This method differs from others in the ability to make some parts for the boat engine with your own hands. This will require a 2-stroke gasoline engine with a cylinder volume of 25 cm3. The engine power from the grass trimmer should not be less than 0.7 kW, and its weight should not be more than 4.5 kg. The unit must be equipped with a bent leg. A grass trimmer engine that meets all these parameters will make it possible to move the boat at a speed of 5 to 8 km / h with minimal fuel consumption. We will describe in more detail the principles of its manufacture below.


This method stands out for its simplicity and economy.

For work you will need to prepare:

make, boat, motor, grass, trimmer

As a rule, there is a ready-made drawing in the set for the screw. This makes it possible to save on the search for the schemes necessary for the operation. The installation of the outboard motor takes approximately 1-1.5 hours.


To assemble a boat ICE, the manufacturer will need to prepare an angular gearbox that can be removed from an angle grinder. Also, for alteration, a propeller is needed. it can be cut from a sheet of stainless steel and bend the resulting blades at the desired angle.

Despite the relatively small pitch of the resulting propeller, this alteration method makes it possible to achieve the maximum possible speed from the engine. The only drawback is the need for additional engine adjustment, for which you can use pliers.

Making a boat motor from a grass trimmer

These days, a common household grass trimmer is more than just a tool for maintaining your garden and garden. It is also the basis for self-assembly of various useful units in the household, the list of which includes a boat motor based on a grass trimmer. One of the main advantages of brushcutter outboard motors is their ease of assembly and ease of maintenance. Thanks to this, even a beginner will be able to cope with the manufacture and operation of a boat internal combustion engine from a grass trimmer.

How to make a do-it-yourself boat motor from a grass trimmer?

To assemble a grass trimmer motor onto a boat, the manufacturer will need to prepare the following equipment and materials:

  • household lawn mower;
  • clamp. If not, you can use any other mount to securely fix the motor on the boat;
  • duralumin sheet, the thickness of which should not be less than 2 mm;
  • welding machine;
  • set of fasteners;
  • set of screwdrivers and wrenches.

The manufacturer will need blueprints to assemble a homemade propeller. They must indicate the exact dimensions of the blades and the way they are fixed on the axis.

It should be remembered that the lower the power of the drive used and the weight of the boat, the smaller the blades should be. For example, for a boat with a mass of no more than 120 kg, a propeller with blades of 10 × 3 cm is suitable.

After preparing the equipment and carefully studying the drawings, you can start assembling homemade products.

The work algorithm should look like this:

Homemade weedeater outboard motor test

  • First of all, the manufacturer will need to modify the bent shaft. First you need to dismantle the factory nut placed in the spool with pre-wound fishing line. The nut itself is shaped like a small 2 cm tube with an internal thread. If necessary, it can be divided into 2 small full-size nuts. When removing fasteners, you need to be extremely careful not to lose them. If this happens, then finding another suitable fastener will no longer work;
  • After dismantling the nut, you will need to dismantle the plastic cover located on the gas button. There are no roller bearings at the end of the standard curved rod. They are replaced by an ordinary bronze bushing, which is often referred to as a sleeve bearing. It must be carefully removed. Before this, you will need to unscrew the nut, and also remove the stern tube and metal shafts from the tube;
  • Then you need to move on to knocking out the plastic protector located on the flexible shaft. In the future, the steel pipe can be thrown away, since it will not be possible to align it with improvised means. It can be replaced with a duralumin tube of the same diameter. You will need to install a bronze bushing in it, which will need to be moved along the canvas with a hammer. Next, you need to take a plastic protector pre-cut in diameter and install it on the pipe;
  • The next step is to make a screw. To do this, you need to cut out duralumin blades and sharpen their edges. After that, each blade will need to be bent up by 1 cm so that the screw pitch is at least 10 cm. You can fix the finished device with a nut;
  • Next, you need to install a bicycle speed switch on the outboard motor from the brushcutter, which will replace the standard plastic cover. After that, you will need to install a muffler that will divert engine exhaust away from the boat driver;
  • To secure the outboard motor from the lawn mower, you need to use two sheets of plywood. After that, it remains to clamp the shaft using 4 screws. When transporting the outboard motor from the grass trimmer, the shaft can be removed.

How to use an outboard motor from a brushcutter correctly?

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

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

  • checking all the mounts available in the device. before each start of the engine, you need to carefully inspect the clips that hold the engine elements from the grass trimmer;
  • refueling 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 air and fuel filter of the engine;
  • regular inspection and timely replacement of the fuel pump;
  • inspection and, if necessary, replacement of the spark plug.

Regular ventilation of its standard cylinder will also help to extend the service life of a boat ICE from a grass trimmer. To do this, approximately once every 2 months, you need to unscrew the spark plug, and rarely pull out the starter cable 4–5 times. After the procedure, the plug can be screwed back into place and continue to operate the engine.

Grass trimmer motor: features

The idea to use something else as a boat engine has occurred to more than one home craftsman. As a result, they learned how to make a motor for a boat with their own hands from a lawn mower, an electric screwdriver, and, of course, a lawn mower. Of course. because the cost of a lawn mower compared to a motor is an order of magnitude less, and the drive power is quite acceptable.

A motor from a grass trimmer is the easiest to make, since the device has all the necessary mechanisms:

  • economical engine. especially when it comes to a four-stroke. In most cases, of course, a two-stroke is used, since its cost is lower;
  • built-in fuel tank, almost always transparent, so that the fuel level is easily controlled;
  • ready-made controls. starter, gas;
  • rod with a rigid shaft that transmits torque.

The only difficulty in reinstalling a motor is the different tasks for which the motors were designed. The drive on the petrol cutter works with high revs and low torque, while the boat drive should do the opposite. Therefore, in order to build a boat motor from a grass trimmer, you will need both tools and blueprints. The photo shows an example of using a lawn mower as a drive.

How to make a homemade boat motor from a grass trimmer

Converting an ordinary boat, even a rubber one, into a motorboat is as easy as shelling pears: you need to install a gasoline engine on it. Electric is not appreciated by our fishermen: a heavy, low power reserve and there is no way to recharge it during a long fishing trip. However, the cost of even the simplest option for a boat is hefty. 20-30 thousand rubles.

Required tools and materials

  • Duralumin for screw, thickness 2 mm.

Weed Eater Boat Motor Build

  • Clamp or other device to secure the engine to the boat.
  • Welding machine. you can do without it only if all the necessary parts are purchased.

Manufacturing technology

Grass trimmer boat motors are made in two ways: all parts, like a propeller, are bought or made by hand. The second solution will require more effort, but also less cost.

As such, the drawing is not needed for the drive itself, but in the manufacture of a homemade screw. The dimensions of the latter depend on the power of the drive and the weight of the boat. A propeller with parameters 10,030 mm is quite capable of moving vehicles weighing up to 120 kg.

  • It is easier and faster to build a boat motor from a grass trimmer if you choose the straight shaft model. If an apparatus with a curved shaft is used. a curved bar, it will have to be almost completely redone, since the steel cable, in principle, cannot transmit the delivery torque. In this case, the tube will need to be made with your own hands from duralumin, then press into it the bronze bushing left after disassembling the bent shaft, and insert the newly fitted plastic holder.
  • A homemade screw is cut from a duralumin plate according to the drawing, the edges are sharpened. The blade should have a curved shape, for this they are bent in turn by 10 mm. The propeller can always be corrected by undercutting or bending more than the blade if its performance during testing turns out to be unsatisfactory.
  • The screw is installed in place of the trimmer head. It is imperative to use a ring nozzle, otherwise the blades may weep or damage the boat material. In the photo. screw fastening.
  • On the Internet, you can find ready-made kits for converting a lawn mower into a watercraft. It includes a drive and shaft adapters. The adapters are universal, which makes it possible to do without reworking the curved rod and shaft. Often a clamp is included in such a kit. In this case, all work comes down to assembling the modification.
  • Control. starter handle, can be used from grass trimmer. But if it is inconvenient, which is often the case, it is replaced with any suitable switch. from a bicycle, for example.
  • Homemade grass trimmer outboard motors are clamped onto the boat transom.

In the video, the process of converting a lawn mower into a boat drive is discussed in more detail.

rubber boat grass trimmer

It is known that fishermen are very resourceful people. If the owner of a rubber boat has a desire to increase the speed of movement of his boat, but there is not enough money for this, then installing a grass trimmer from a lawn mower will help while the cost of a lawn mower is much less. Grass trimmer power is quite decent for a rubber boat.

Advantages of the grass trimmer when mounted on a rubber boat:

Beginner fishermen have questions about installing the device on their boat.

Can I put a grass trimmer on a rubber boat

The answer to this question is yes, you can. This is an inexpensive (compared to a full-fledged outboard motor) way to increase the speed of movement in a pond than buying a full-fledged motor. To use the lawn mower grass trimmer as a boat engine, it needs to be slightly upgraded. There are two ways to prepare the apparatus for installation on a rubber boat. The first way is to purchase special attachments, and the second is to make them yourself. The ready-made set of accessories solves all your difficulties with installing the grass trimmer on the boat. This set usually includes:

Propeller screw; 2. Attachment attachment. Represents the lower part of the outboard motor (no engine) to which the lawn mower grass trimmer is attached; 3. Adapters for installing different types of trimmers; 4. Tiller. handle for control. Equipped with a muffler button; 5. Clamp. It attaches the grass trimmer to the transom of the boat.

Self-production of a grass trimmer is possible using a motor from a lawn mower with a straight bar and a rigid shaft. To do this, you only need to make a propeller. The raw material for manufacturing can be stainless steel or duralumin. The blades must be bent, the edges of the screw must be sharpened. If a motor with a bent shaft is used, it will have to be completely redone and will take much longer.

Using the motor from a rubber boat lawn mower

When operating a motor from a lawn mower as a rubber boat engine, you must follow the rules:

Should you buy a grass trimmer attachment to a boat motor?

It is impossible to give an unambiguous answer to this question, since someone is very accustomed to motors on boats, while others have never used them. At the same time, if you want a really powerful boat for yourself, then naturally the most profitable and effective solution would be to install a standard grass trimmer. But it should be borne in mind that this option is universal. As mentioned above, the most important thing is to correctly combine.

Many experts recommend blades similar to those of your old motor. It is very important that it is necessary to install in strict accordance with the instructions.

In addition, you should pay attention to the moment that you definitely need to take additional fuel with you, and just like an ordinary lawn mower, you should be given the opportunity to “rest” because, due to very long use, the grass trimmer-motor may simply come out of building right on the water.

The larger the blades, the more effective the grass trimmer will be.

Alteration of brushcutters is as follows:

Initially, the main bent shaft is being altered: first, a standard nut is removed from the reel with a special fishing line. It is a small tube, the length of which is 20 mm.

At the same time, the nut must be preserved, since the thread on the brushcutters is extraordinary and it is almost impossible to find the same.

Then the plastic cover with the keys is removed. After that, at the very end of the bent pipe itself there is a standard bronze bushing (often called a sleeve bearing). it must be carefully cut out, after that you need to remove the stern shaft, unscrew the nut and the metal shaft.

The most important thing is to choose the right blades. Everything here directly depends on what dimensions your boat has.

boat outboard made from a weed whacker

Here it is very important to pay attention to the factor that the best solution would be to enter “motors on a boat” in the search and on the first site you come across go to the site where motors are sold and ask a question to a consultant who will offer you his help. you say the dimensions of your own car, and then, when you get a suitable engine, you need to look at the technical characteristics and find out the dimensions of the blades.

What is outboard motor grass trimmer attachment?

The idea of ​​a very light outboard motor for small boats, including the simplest ones. rubber today is of interest to many hunters and fishermen. It is important to note that the cost of such a motor is quite high and maintenance, as well as parts. In this case, many very often began to use motor grass trimmers, which are now very popular and widespread.

Principle of operation

The grass trimmer has a higher blade speed, which allows you to move at a higher speed in the water, which will allow you to start fishing faster than with a motor. Everyone saw how a grass trimmer works. how it cuts a lawn and ordinary grass, but here, its blades are turned in the other direction and at the same time, it performs the function of the most economical motor.

However, if the grass trimmer is lower, the speed will be lower. But the main disadvantage of the trimmer compared to ordinary outboard motors is that they are very loud and should not be used to their fullest if you do not want to frighten off the fish.

Trimmer benefits

Many will naturally ask why a grass trimmer. It has a number of undeniable advantages:

  • easy;
  • comfortable;
  • economical;
  • very powerful;
  • has the main controls: starter, throttle;
  • complemented by a specially “leg” that allows you to adjust the power.