How to make a grass trimmer into a motor for a boat

Transform Grass Cutter Machine Into Rudder Boat Propeller Drive

Features of a homemade engine

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

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

  • A very economical motor;
  • mounted unpainted fuel tank, which allows you to easily control the amount of fuel;
  • The presence in the device of a starter and gas;
  • 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 motor for the boat.

make, grass, trimmer, motor

Grass trimmer functions at high revolutions and a small torque, and the boat motor should do the opposite

What you can make

There are several possible options for refinement of the grass trimmer under the motor for the boater.

Take it as a rule, on every fishing trip, the first thing to start.

Homemade weedeater outboard build water test

A very simple method, but requires additional financial costs.

You will need to buy these parts:

  • Clamping clamp for attaching the device to the boat transom.
  • Propeller. You can buy a ready-made kit online, as stores may not have this kind of product. The set includes 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 will fit your model of lawnmower or not.

Tip! Sometimes a clamp may be included, so check before you buy it to see what’s included.

A drawing of the trimmer mount is in the manual. You will need about half an hour for installation.

For modification you will need an angle reducer 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 propeller. In the field, the device requires additional adjustment, which is done with a pair of 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 of 25 cm3. The 700 watt, 4.5 kg device is equipped with a bent leg. the grass trimmer with such power allows the boat to move at a speed of about 5-7 km/h.

For this method you need an angle gearbox from an angle grinder, a screw, which can be cut from a sheet of stainless steel, as well as seals and bearings for fastening

What will be needed

For making it, you need materials as well as tools:

  • Lawn trimmer.
  • Duralumin with a thickness of 2 mm. It is necessary for the propeller.
  • Screw clamp or any other device for attaching the device to the boat.
  • Apparatus for welding.
  • Fixing elements.
  • Additional tools for work.

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

Fabrication Instructions

To make a boat engine out of a regular grass trimmer you will need to do the following:

    Never discard or lose the nuts, as the developer companies use their own type of thread, which is not metric or inch
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Rebuild a bent shaft. To do this, you must remove the original nut, which is located in the spool with the line. It looks like a small tube of 2 cm length and has an internal thread. It can be split into two complete nuts. Tip! Never throw away or lose any nuts, as the developer companies use their own type of thread, which is not metric or inch. Next, you need to remove the plastic overlay, which is on the throttle button. At the end of the bent rod there are no roller bearings, instead there is an ordinary sleeve made of bronze, also known as a plain bearing, it must be removed. To do this you need to carefully cut it, first unscrew the nut and remove the metal and stern shaft from the tube. Freed from the bronze sleeve, you can proceed to knock out the tread of the flexible shaft, which is made of plastic. Tip! The steel tube can be thrown away, because it can not be aligned. Instead we use a duralumin pipe with the appropriate diameter. Mount the bronze sleeve in the duralumin pipe and press it carefully into the pipe with a hammer. Then take the plastic protector, trim it a little in diameter and mount it tightly in the tube. Tip! When the outer diameter of the tube is larger and does not fit into the mounting hole on the motor head, you will need to mill it to the correct size. If necessary you can build a longer shaft using a tube of desired length, and install a steel bar instead of the flexible shaft of desired length.

For the running-in of the homemade engine you will need a tank of gasoline (0.5 l.) with oil in a ratio of 1:40. One tank of fuel can overcome about 10 km of territory. 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.

Devices with a double-sided flywheel

Grass trimmer conversion into a boat motor with a double-sided flywheel is pretty simple. A screw for this should be chosen of small diameter. Grass trimmer is suitable with a manual regulator and low power. Start the assembly by fixing the stand.

If we talk about the simple model, the starter does not need to be touched. When assembling the deadwood it is important to pay attention to the connector fixation. The screw is installed on the rack last. Hand wheel for the purpose of changing the position of the pipe is mounted behind the starter. It is very easy to operate these motors. To prevent water from getting on the connector, various covers are used.

How to Make a Homemade Boat Motor from a Grass Trimmer

To remake an ordinary boat, even a rubber one, into a motorboat is easy: you need to install a gasoline engine on it. Our electric is not valued by our fishermen: heavy, small power reserve and there is no way to recharge it during a long fishing trip. But the cost of even the simplest variant for a boat is pretty hefty. 20-30 thousand. р.

Advantages and peculiarities of converting grass trimmer into a boat motor

The use of a lawn mower available in the farm has a number of advantages. First, the boat owner will not overpay for a store-bought, expensive motor. Secondly, a motor for a boat from a brushcutter consumes much less fuel than specialized boat engines. Thirdly, a lawn trimmer engine has an order of magnitude smaller dimensions than a store-bought boat motor. There are a number of other factors that force fishermen to use a grass trimmer instead of a boat motor.

  • The high reliability of modern trimmer engines;
  • complete tightness inside the hull;
  • The availability of all the elements necessary to control a homemade engine;
  • the presence of a built-in tank.

Thanks to all these factors, a boat motor from a brushcutter is the most popular among enthusiasts.

In the process of recycling an engine from a lawnmower into a boat motor, it is extremely important to take into account that this power unit was produced for other purposes. The engines on trimmers run at low torques, but, at quite high revolutions. In the case of a specialized boat engine, everything is the opposite. In this regard, to redesign the motor from a trimmer for grass will need to prepare drawings, equipment and follow a certain order of action.

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Despite some difficulties in remaking, it is in the trimmer there are all the parts necessary for making a boat motor. a built-in starter and throttle lever, a rod with a rigid shaft and a semi-transparent fuel tank.

Methods of making a boat engine from a brushcutter

The easiest way to make a motor for a watercraft is to use a brushcutter with a straight leg (rod) and, accordingly, a rigid shaft. In this case all completion is reduced to the production of a propeller, which can be cut from a strip of stainless steel or duralumin. The size of the workpiece. 100x30x2 mm. Blades should be given a bent shape, for what they need to bend by about 10 mm. The edges of the propeller need to be sharpened. An example of a simplified drawing of a propeller is shown on the picture below.

Important! Dimensions, number of blades and their bending angle are selected individually, based on the weight and size parameters of the boat and engine power of the grass trimmer.

The manufactured propeller is installed in place of the trimmer head. In this case, it will be desirable to use a ring nozzle, which will not allow the propeller to damage the boat. In more detail the process of refinement of the grass trimmer with your own hands is shown on

boat outboard made from a weed whacker

Improvement of the angle grinder gearbox

To achieve the maximum engine speed, the grass trimmer can be equipped with an angle grinder reducer, which must be modified beforehand. Oil seals and bearings may be needed. The process of gearbox improvement consists in replacing the short shaft with a longer one, corresponding to the size of the grass trimmer shaft. However, to do this, you will have to disassemble the gearbox.

Important! Shape and mounting dimensions of the new shaft must match the parameters of the unit removed from the gearbox. This, in turn, will allow the use of available bearings and gears in the gearbox.

After making a new shaft, the gearbox is assembled, having previously protected the bearing with an oil seal that prevents water from penetrating into it. In addition, it is recommended to apply thick grease to the existing gears or fill the inner cavity of the housing with it. To seal the body use a rubber seal and / or sealant.

Please note! Increase the trimmer motor speed through the gearbox and mount the propeller on the gearbox output shaft.

Modification of grass trimmer with bent boom

If the boat owner has a lawn mower with a curved boom, the latter must be dismantled and replaced with a straight tube of the appropriate diameter, made of duralumin. If the diameter of the new tube will be larger than the size of the hole in the engine block, the landing place will need to be turned down to the right size. Please carry out the rework in the following order (see drawing). drawing).

  • first unscrew the standard nut 2, which is located in the bobbin with cord. Do not throw out the fasteners previously removed from the upper shaft, as brushcutter producers often use their own threaded fasteners that do not fit the standard ones.
  • Then unscrew the nut 4 and remove the stern tube (item 9). 8) and flexible (pos.9) shaft.
  • Then the sliding bearing 6 is cut out (this has the shape of a bronze sleeve at the end of the shaft).
  • Then knock out of the rod plastic protector 10.
  • In a selected beforehand straight pipe 7 press out the previously extracted plain bearing 6. It may be necessary to bore out the tube for this.
  • Then the slide bearing 6 is carefully pressed with a hammer on the groove 5. Here it is important not to damage the pressed bronze bush.
  • Then the plastic tread 10 is cut to fit and slid tightly into the tube 7.
  • Then the stern shaft is connected to the steel bar, which will replace the flexible shaft 9. This may require the help of a turner.
  • The final step. the propeller 3 is attached to the stern shaft 8 with the nut 2.

The assembled boom is connected to the motor using specially made adapters, the shape and size of which depend on the design features of a particular model of grass trimmer.

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Working Principle

A motor for a grass trimmer boat has a higher revolving speed of the blades, which allows you to go faster on the river. When the gasoline mower works when mowing the lawn, its blades are reversed. When making a motor for a boat, the motor blades are inverted. Then the motor will work to push the boat. The higher to the surface of the water, the faster the blades are, the faster the speed of the boat.

Make a motorcycle with their own hands from a lawnmower is not as difficult as it may seem at first glance. First determine how much power is the engine on the trimmer. It should have at least 2 horsepower. Otherwise the future machine won’t be able to travel long distances or even move at all.

The next step is to design the drive. You will need to make a leading pulley (attached to the motor), a driven pulley and a special frame for the motor. The belt that transmits the torque is recommended to be selected at the end of the assembly, based on the dimensions of the entire structure.

Install the engine from the grass trimmer on the bike can be made by making a special small frame of scrap metal at hand. The second point is the attachment of this structure to the bicycle. It should be reliable and at the same time convenient in terms of maintenance. This suspension should be mounted securely, be resistant to vibration and, preferably, quickly and easily disconnected.

There are two mounting options:

Each method has its pros and cons. Take into account all the peculiarities of your equipment and its operating conditions, and proceed from these data when choosing a mounting option.

Additionally, do not forget to attach details such as a small fuel tank, exhaust pipe. Not superfluous will also be the installation of an additional brake, since a bicycle with an engine from a grass trimmer will be much faster and more powerful than the usual one.

We suggest that you also read the video, which shows the process of constructing a motorcycle from a trimmer for grass:

Remaking: a motor for a boat on the basis of a trimmer for grass

Any fisherman who has an inflatable boat, sooner or later starts thinking about buying a motor for it. But, having learned the price for ready-made solutions, many begin to look for alternative engine options for their watercraft. Fortunately, folk craftsmen have already invented, how to remake lawnmower, electric screwdriver or lawnmower in the boat motor. But the best option for this purpose is a gasoline grass trimmer that has all the necessary mechanisms and elements.

Gearbox and its effect on operation

Using the reducer for a boat motor makes it possible to change the direction of axial rotation. The reducer changes the shaft speed by several times, which positively affects the engine operating life. When equipping a gearbox for a boat motor, you should adhere to the golden mean and not put a device with a large gear ratio. Failure to do so will result in excessive fuel consumption, slow boat speed, and engine overheating. The surest way to install a gearbox with an optimum ratio for a given engine is to try out several different units. If you will not feel the excessive load, which manifests itself in the inability to quickly reach high speeds and the speed of the watercraft will be rather high, then this gear ratio can be considered as optimal for the engine.

An average transmission ratio that will work well with many internal combustion engines used as a boat motor is 1/5.

Electric motors can be used as thrust for boats without a gearbox. The pulling power of such devices is enough to work steadily in direct transmission of torque to the propeller. A great engineering solution is to use the electric motor underwater. With this arrangement, the propeller is attached directly to the shaft of the electric motor.

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