Possession boat-engine 5 horsepower is often a compromise between the desire to save on the registration of a boat in the GIMS and the need for normal speed on the water. Owners of such units often face a situation when the engine “does not pull” two adults or glides are difficult, which is why the topic of how to swell a 5 liter outboard motor with video remains one of the most popular in the boating community.
Modern two-stroke engines of Chinese production (Tohatsu, Mercury, HDX, Sea-Pro) are originally designed as a single platform for power from 2.5 to 9.8 hp The difference often lies only in the presence or absence of physical limitations: milling in the exhaust pipe, plugs in the carburetor or modified gas distribution phases. Frost It allows the engine to return its natural power, but requires accuracy.
In this article, we will discuss the technical aspects of the refinement, touch on the legal nuances and assess the real risks to the engine life. Modifications It should be carried out consciously, with a clear understanding of the combustion processes of the fuel mixture.
Legal aspects and risks of revision
Under current regulations, a small vessel with an outboard motor up to 8 kW (about 10.8 hp) does not require registration with the GIMS if its weight does not exceed 200 kg. However, inspectors can take power measurements on the stand if doubt arises.
⚠️ Warning: Operating an unregistered engined vessel with an actual power of more than 10 hp will result in fines and delays until violations are corrected. If you are caught with a smothered engine and its actual power is higher than the permitted without a license, the problems will be serious.
Technically, the removal of the restrictions results in the engine operating in modes that it may not have expected the manufacturer to perform as standard. consequences The engine life of 5 hp after scattering can be reduced by 20-30%.
However, many aqueous engines are taking this step: often owners buy the engine with the expectation of future fragrance, choosing models that are structurally identical to the 8-10 strong versions, the key here is the quality of the build and the materials used, which directly affects the durability.
Principal scheme of power limitations
To understand how to suffocate an outboard motor, you need to know where exactly the manufacturer is suffocating power. In most cases, Chinese copies of Tohatsu use three main methods of limiting. cutter It's a metal washer or constriction that keeps the gases from flowing out freely, creating backpressure.
The second method is to limit the flow of the fuel-air mixture through the carburetor, which can be a plug in the jellybar or a throttle limiter; the third option, which is less common at low power, but is possible - changing the timing phases (the height of the lobe valve lift) or using a switch with a limited speed.
It is important to note that simply removing the milling cutter, you will not get a two-fold increase in power without the appropriate carburettor settingsPoor mixture with an open flap can cause the piston to burn, so a comprehensive approach is the only solution for safe operation.
| Method of limitation | Location. | Difficulty withdrawal | Resource impact |
|---|---|---|---|
| Freshman in the exhaust | Under the muffler/dadewood | Medium | Minimum |
| Carburettor stub | Inside the carburetor | High. | Medium (requires settings) |
| Petal valve | Intake manifold | High. | High (CNG wear) |
Tool preparation and dismantling of lower unit
You'll need a standard set of tools to get started, and you'll need to prepare a set of heads, a rattle, flat screwdrivers, cross screwdrivers, and passages. sealant for subsequent assembly and WD-40 for processing sour bolts.
The process starts with the fuel hose being detached and the motor being removed from the transom. Turn the engine into a comfortable position, providing a steady stop. The first thing you need to do is unscrew the bolts that attach the lower unit (foot) to the lower unit (the middle part with the engine), which are usually 4 or 6 pieces, they can be of different lengths, so remember their location.
Once the fastener is unscrewed, the lower unit is gently removed down, so it's important not to damage the thrust of the speed switch and the water pump rod. In some models, the thrust of the switch is fixed by the stopper that needs to be removed. Stoke pump. Usually just comes out of the rubber clutch with careful swaying.
☑️ Ready to disassemble
Removal of the cutter and refinement of the exhaust system
The most efficient and safest way to add power is to remove the milling cutter from the exhaust pipe. When you take a lower unit, look at the bottom of the cylinder block, and you'll see the exhaust windows closed by a metal plate or a narrowed channel, and that's the narrowing that is the milling.
It's often enough to just knock or drill a jumper out of the window, but be careful that the shavings don't get inside the cylinder or the crankcase, and it's best to clean the channel carefully so that it's the diameter of the cylinder exhaust window. counterpressure It'll improve the purge.
Some experts recommend completely replacing the exhaust washer with a counterpart from a more powerful model (for example, from 9.8 hp) if it is available on sale. This is a more aesthetic solution than rough drilling. After the procedure, be sure to blow the channel with compressed air to remove any metal particles.
What happens if you don't remove the cutter?
If you leave the milling cutter and just add fuel, the engine will run on a rich mixture, coking candles and losing power.
Setting up the carburetor and fuel system
Once the exhaust is "unpacked," the engine will need more fuel to create a powerful mix. The standard 5 hp carburetor setting is too poor for full power. You'll need access to the carburetor itself, which is usually located under the air filter cover.
Remove the filter cover and find the adjusting screws. We're interested in the mix quality screw (usually it limits the throttle or has a stopper). Many Chinese motors have a plastic plug or washer that prevents the valve from opening completely, and it needs to be carefully removed, ensuring that the cable gas is fully rotated.
Then you have to adjust the L (Low) and H (High) screws to the point (not much!), then spin the screws to the point (not much!), then twist 1-1.5 as the basic setting. Start the engine and warm up will show the result. If the engine stalls at sharp gas, the mixture is poor (twisting the H screw), if it chokes and smokes - rich (twisting).
When you first adjust the carburetor after scattering, do not more than 1/4 revolution with a quality screw at a time. The engine should warm up 2-3 minutes before each check.
Installation of a petal valve: is sheepskin worth making?
More advanced tuning involves replacing or refining the petal valve. In the runoff on 5-horsepower engines, the petals can be rigid or have a travel limiter. Installation of softer petals (for example, from Yamaha or specialized tuning firms) improves the filling capacity of the cylinder at low and medium revs.
The process requires a complete disassembly of the intake manifold, petals must fit tightly to the body, but can be easily opened under the pressure of the mixture, a loose fit will lead to the back ejection of the mixture and unstable idling. tuningIt's a skill-driven thing.
The effect of this modification is seen primarily on thrust, the boat is faster to glid, better holds the wave, but the life of the petal knot may decrease, as softer materials tire more quickly from constant impacts.
⚠️ Warning: When installing non-original petals, make sure that they do not touch the intake wall when fully opened. A broken petal, once in the cylinder, is guaranteed to disable the engine.
breaking in and final system check
After all the manipulations, the motor must be assembled using a new layer of sealant at the junction of the crankcase and lower unit. Tighten the bolts cross-to-cross to avoid distortion. Before the first start, be sure to check the cooling system: connect the water supply hose or lower the motor into the barrel.
Start the engine and let it run at idle speeds for 5-10 minutes, monitor the temperature of the cylinder head and the presence of "parasitic" vibrations, if everything went smoothly, you can run a test run. Start at low speeds, gradually increasing the load. The first 2-3 tanks of fuel are considered the period of increment of new settings.
When you run the car, listen carefully to the engine, if you ring or knock, you're going to have too little mixture or too much heat, and then you have to stop running and reconfigure the carburetor immediately, and if you blow it properly, you're going to sound evener and more confident than you would in the runoff.
The main result of the scent: removing the cutter gives +30-40% of power, adjusting the carburetor adds another 10-15%, but requires accuracy. Without tuning the carb, the scent is useless.
Will the fuel consumption increase after the swelling?
The consumption will increase, but not in proportion to the power. It will hardly change on singles. Under load (planing), the consumption will increase by 15-20%, since the engine will run in a more efficient mode, rather than choking.
Can I swell the engine 5 hp to 20 hp?
No. Structurally, the cylinder block, the crank-shaft mechanism and the cooling system of 5-strong power units are designed for a certain thermal regime. Exceeding power by more than 2 times (up to 10 hp) is the safety limit. Further increase will lead to rapid engine destruction.
Should I change the candle after finishing?
After scenting and adjusting the carburetor, the thermal regime may change, and it is recommended to use candles with the potassium number recommended for 8-10 strong versions of this engine (usually slightly colder candles) to avoid kalyl ignition.