Tuning of the outboard motor from the trimmer: a step-by-step guide

The idea of turning a regular garden trimmer into a full-fledged outboard motor attracts many fishermen and summer residents looking for budget solutions for their boats. Unlike factory models, which can cost a significant part of the budget, a homemade unit costs many times less, especially if the farm already has unnecessary gas jelly. internal combustion engines.

The main attraction of such tuning lies in the versatility and availability of spare parts. Two-stroke enginesThe only difference is the way to transfer torque and the cooling system, and if you're willing to spend a few days experimenting, the result might surprise you with its efficiency on lightweight inflatable boats.

Now, it's worth noting that building this kind of mechanism is not just a shaft connection, it's a complex engineering challenge, and you're going to have to deal with the issues of sealing, alignment and, most importantly, safety. screw or poorly fixed design can lead to failure at the most inopportune time, so each stage should be approached with maximum responsibility.

Choosing a donor: which trimmer is best

The first and most important step is to choose the original unit, not every benzokot can turn into a reliable propulsion system. pole-barThe torque is transmitted through a rigid shaft, not a flexible cable, and the flexible shaft that is characteristic of curved rods will not withstand the loads of water resistance and quickly fail, turning into useless wire.

Pay attention to the power of the engine. For a boat with one man and a small load to move confidently, the minimum power must be 1.5 to 2 horsepower. Weaker models designed only to trim the grass can simply stall under load or overheat. Stihl, Husqvarna and their high-quality Chinese analogues with an engine capacity of about 30-40 cubic centimeters.

⚠️ Warning: Air-cooled engines designed for air operation may overheat in a closed space in a lower unit, and air must be supplied to the cylinder or additional water cooling should long-term high-speed operation be planned.

The clutch is also critical, and the centrifugal clutch that automatically turns on when you set speeds is ideal for an outboard motor, which will allow you to start the engine at idle speeds without rotating the screw, which greatly simplifies control and improves safety when you board the boat.

• 🔧 Look for models with a collapsible gearbox at the end of the bar – this will make it easier to replace gears.
• 🔧 Check the condition of the piston group: compression should be excellent, since the load on the water is higher than when cutting grass.
• 🔧 Make sure the carburetor is adjustable, rather than having factory plugs on the mix quality screws.

If you plan to use the engine on a heavy boat, it makes sense to consider the option of sparkling two engines, although this greatly complicates the design and requires the creation of a frame.

Required tools and materials for remodeling

Before you start dismantling, you need to prepare the workplace and tools, you need not only a standard set of keys, but also specialized equipment for metal processing, pay special attention to protection, because working with metal and fuel requires caution. Without a quality tool, you will not be able to build a reliable unit.

The main list of tools includes a grinding machine (Bulgarka) with metal discs, a welding machine (preferably argon or semi-automatic for thin metals), a drill with a set of metal drills and a measuring tool. Accuracy plays a crucial role here: the slightest distortion of the shaft will lead to vibration and destruction of bearings.

From materials, you will need a steel sheet 2-3 mm thick to make a mount (transe adapter), a segment of the pipe for the lower unit (if you do not use the native trimmer bar), and a waterproof sealant.

It is worth mentioning separately about lower unit You can use the native trimmer pipe, cutting it at the desired length, or make a new one from an aluminum or steel pipe with a diameter of 20-30 mm, the main thing is that the inner space allows the shaft to rotate freely and, if necessary, water for cooling.

Manufacture of transom fastening and lower unit

The most critical step is to create a motor attachment unit to the boat, and this is the element that handles all the loads when moving and has to be done with a margin of safety, the design is a plate that presses against the transom of the boat, and a vertical pipe in which the engine is attached.

To make a mount, take a sheet of aluminum or steel. The shape of the plate should be the same as the transom configuration of your boat, and the height of the engine should be adjusted. Often, a system of grooves and bolts is used to raise or lower lower unit, choosing the optimal angle of attack of the screw, this is especially important for shallow water.

Thickness of metal for fastening: not less than 3 mm
Diameter of lower unit: 25-30 mm
Height of the screw lift: adjustable (100-300 mm)

The engine is attached to the top end of the lower unit, and it's important to keep the joint tight so that the spray doesn't get on the carburetor and the air filter, you can use rubber pads or cuffs from car oils, and the engine shaft must be strictly aligned with the screw shaft, otherwise the vibration will destroy the structure.

⚠️ Warning: When welding a fastener plate, avoid warping the metal. If you use steel, be sure to treat the seams with corrosion-resistant composition and paint, otherwise the rust will eat the fastener in one season.

Some craftsmen make the mounting rotary by adding a hinge assembly, which allows you to control the boat by turning the handle of gas, like on factory engines. However, for the first experience, it is easier to make a fixed version with control through a rod fixed to the bar itself.

Modernization of the gearbox and installation of the propeller

The native trimmer gearbox usually has a gear ratio designed to work with a knife or line, rather than overcoming water resistance. The boat requires changing the gear ratio to increase thrust. Often requires replacing gears with more suitable gears or using a ready gearbox from an old outboard motor, for example, from an old outboard motor. "The Wind" or "Salute.".

If you leave your own gearbox, make sure that the output shafts are well protected from water. The trimmer's coils are not designed for constant immersion. They should be replaced with anther cuffs designed to work in an aqueous environment. The lubricant in the gearbox should also be replaced with water resistant, for example, lithium or specialized for outboard motors.

Parameter	Standard trimmer	outboard motor	Recommendation for tuning
Transfer ratio	1:1.5 - 1:2	1:2 - 1:2.5	Replace gears or use an external gearbox
Type of lubricant	Plastic (lithium)	Water resistant (calcium sulfanate)	Use only waterproof lubricant
Shaft protection	Weak.	Tall (salnicks)	Install a double oil oil oil oil oil oil oil
Screw material	Plastic/Steel	Aluminum/Stainless steel	Use aluminum screws of stepping type

The choice of propeller is a separate science. The diameter and pitch of the screw are selected experimentally. Too large screw will "strangle" the engine, and it will not gain momentum, too small will not give the desired traction. The optimal way to start with a screw with a diameter of 150-180 mm and a step of 100-120 mm. The screw is usually fastened on a cone shaft with a nut and a splint.

Where can I get a screw?

You can find propellers in outboard motor stores, in auto-disassembly (from old engines), or make them yourself from sheet duralinium if you have the skills to work with metal.

Configuring the fuel system and carburetor

After mechanical assembly, it is time to adjust the heart of the engine, the trimmer carburetor is designed to work in a horizontal or slightly inclined position, and when you vertically install the outboard motor, you can have problems with the supply of fuel, especially if the float in the float chamber is stained.

In most cases, a standard carburetor Walbro or ZamaThe trimmer is going to work normally and upright, but you may need to adjust. You need to set up three screws. L (low revs), H (high turnover) and T The mixture should be slightly richer on water than on air to avoid overheating and to ensure stable traction.

It's important to keep the fuel hoses tight. Gasoline doesn't get into the water, air doesn't get into the fuel system. Use high-quality gas-resistant hoses and tighten the clamps. The fuel filter in the tank also has to be clean, otherwise the engine will stall at high speeds.

• ⛽ Wash the carburetor with ultrasound or special fluid before installation.
• ⛽ Replace fuel hoses if they are cracked or petrified.
• ⛽ Check the work of the accelerator pump (if any), it should beat the jet when the throttle is sharply opened.

If the engine is unstable, try replacing the jellyplates with slightly larger ones. In water, the engine requires more energy, and a poor mixture can lead to a burnout of the piston. But don't overdo it: too rich a mixture will lead to increased fuel consumption and soaking on the candle.

Operational features and safety

Operating a homemade motor requires increased vigilance. Unlike factory crash-tested products, your design is experimental. Always carry spare mounts and tools. Vibration can weaken threaded connections, so check the tightening of all bolts and nuts before each trip.

Pay special attention to the cooling system. If you haven't water-cooled, watch the cylinder temperature. If you run at full gas in hot weather for long periods, the engine can overheat. Periodically discharge the gas to let the engine cool down, or force the cylinder to blow.

⚠️ Warning: Never run the motor out of water "dry" for more than a few seconds. the absence of load on the propeller will lead to an instant set of limiting revolutions and the destruction of the shaky-piston group.

Don't forget about environmental safety. Two-stroke engines run on a mixture of gasoline and oil, releasing exhaust gases directly into the water or the atmosphere above the water. Try not to refuel directly on the shore so that the fuel does not get into the reservoir. Use funnels with mesh filters.

Store the engine in a dry place, necessarily draining the residue of fuel from the carburetor. Gasoline eventually oxidizes and forms a resinous plaque that will clog the jellyplants. If the engine is not planned to be used for more than a month, it is better to develop the remaining fuel until the engine stops completely.

Frequently Asked Questions (FAQ)

What speed can a boat with a trimmer engine develop?

With an engine capacity of 2 hp, an inflatable boat up to 3 meters long with one person on board will reach a speed of about 5-7 km / h. This is not a racing speed, but quite sufficient for quiet movement on a reservoir and fishing in calm.

Can I use a four-stroke trimmer engine?

Theoretically, it's possible, but it's more complicated. 4-strokes have a crankcase oil lubrication system, and when you tilt it too much (which happens on the wavelength), the oil can move away from the oil intake, which will lead to bullies, and they're heavier and more overall than two-stroke counterparts.

Do I need to register such a motor in the GIMS?

According to Russian legislation, small vessels with an engine of more than 8 kW (about 10.8 hp) are subject to registration. Trimmer engines usually have a power of up to 2-3 hp, so they do not require registration and the availability of driving rights.

Why does the engine stop when the gas is opened?

It's probably the carburetor that's too poor at high speeds, or the fuel filter is clogged, and it could be the air sucker through the crankshaft coils, and check the inlet air tightness.