Any owner of water equipment, whether it is a powerful Yamaha F250 compact Tohatsu 9.8Sooner or later, it faces the inevitable wear and tear of the nodes, and in the process of combustion, the fuel-air mixture forms solid combustion products known as soda on the walls of cylinders, pistons and valves. The accumulation of these deposits A natural process that is greatly accelerated by using low-quality fuels or by disrupting operating temperatures.
Ignoring the problem leads to the fact that compression The engine starts to run unevenly, losing traction at low speeds, which is critical when you get on plane a laden boat. mechanical from detonation can be fatal for the piston group, if the service is not carried out in time.
In this article, we will discuss effective ways to combat pollution without resorting to a complete disassembly of the engine. Chemical decoking Preventive measures will help to extend your life. outboard motor Avoid costly repairs in the workshop.
Causes of the formation of soot and its effect on the engine
The main cause of solid deposits is incomplete combustion of the fuel mixture, and in two-stroke outboard motors, the situation is aggravated by the presence of oil in gasoline. proportion Cheap mineral oil is broken or used, it does not burn completely, forming a viscous substance that at high temperatures turns into coke.
In addition, long-term work at idle speeds or, conversely, constant operation in the “full gas” mode without periodic thrust discharge contribute to the development of the system. ring-shoppingWhen the rings lose mobility, they stop effectively removing oil from the cylinder walls, which leads to even more gas and oil scorching.
The effect of coke on the engine is devastating and multifaceted, and the deposits reduce the volume of the combustion chamber, which increases the degree of compression and causes detonation. The critical point is the occurrence of piston rings, which can lead to bullies and wedges of the engine.
⚠️ Note: Using fuels with an octane number below the manufacturer's recommended (e.g., AI-92 instead of AI-95) dramatically increases the rate of soaking and the risk of detonation.
The cooling system should also be considered. thermostat It's malfunctioning, the engine is working at a lower temperature, the mixture burns worse, speeding up the pollution process, and overheating caused by a clogged cooling shirt causes the oil to burn and hard crusts to form on hot parts.
Symptoms of coking: when it is time to clean the engine
The need for cleaning can be determined by a number of indirect signs that are manifested in the behavior of the boat on the water. loss: the boat reluctantly goes to the plane, and the maximum speed is noticeably reduced even with a fully open throttle.
Another obvious symptom is difficulty starting, especially "hot": the engine can catch, but stall or work intermittently at idle. Floating speeds often indicate that the nagar has violated the tightness of the valves or interferes with the normal operation of the throttle.
Visual inspection also provides a lot of information, and if there's gray or black smoke coming out of the exhaust pipe, it's a direct sign of combustion problems. Ignition plugs in this state will be covered with a black velvety coating or, conversely, have a whitish tint and a melted electrode.
To systematize the signs, the following diagnostic table can be used:
| A symptom. | Probable cause | Risk level |
|---|---|---|
| Difficult launch "to hot" | Compression drop, flap swelling. | High. |
| Knocking at a sharp opening of the throttle | Detonation due to reduced camera volume | Critical |
| Increased oil consumption | Positioning of piston rings | Medium |
| Unstable idling | Sucking air or soak in the channel XX | Low. |
If you experience at least two of these symptoms, it is recommended to diagnose compression. Compression measurement It will show the actual state of the cylinder and help you decide on the cleaning method.
Chemical decoking: choice of means and technology
The most popular and affordable method of cleaning without disassembly is chemical decoking, the essence of which is to pour a special aggressive solvent directly into the cylinders through the candle holes. Active substances soften the solid soak, turning it into a liquid porridge, which then burns out or is removed when scrolling the engine.
For outboard motors, it is important to choose products that not only clean, but also have lubricating properties so as not to damage cylinder mirrors. Lavr, Shumma or GreenolThey offer compounds of varying degrees of aggressiveness, and for prevention, "soft" decoking, added to fuel, and for treatment, "hard" direct-acting liquids, are suitable.
The procedure requires strict adherence to the instructions. The engine must be warmed to operating temperature, twist the candles and pour the composition into each cylinder. After that, the engine is left for a certain time (usually from 1 to 12 hours), periodically scrolling the crankshaft with the starter.
Before starting the engine after decoking, be sure to unscrew the candles and turn the engine several times with a starter to knock out the remaining liquid from the cylinders.
If the rings have already been laid mechanically or the soda has turned into a ceramic crust, the "magic liquid" may not cope. mechanical cleaning Or replacing parts.
Mechanical cleaning and maintenance of nodes
When the chemistry is powerless, mechanics come into play, a method that involves either partial or complete disassembly of the engine, most often requiring the removal of the cylinder head (CBG) for visual inspection and manual cleaning of combustion chambers. Mechanical removal soda is made by special brushes, scrapers of soft metal or chemically mechanically using rags.
Special attention should be paid to the throttle and intake manifold. GR (if designed) is also prone to soot fouling, and pollution disrupts the mixture, making it too rich.
To clean the throttle, use special carburettor aerosols, which effectively dissolve oily deposits. System flushing The intake allows you to restore the correct airflow and stabilize the idle.
☑️ Checklist for mechanical cleaning
⚠️ Attention: When mechanically cleaning pistons, it is strictly forbidden to use sharp metal objects (screwdrivers, knives) that can leave scratches on aluminum. Any scratch will become a focus of further nagaroformation.
After assembly of the engine you need to break-in or at least intensive operation in a gentle mode, so that new surfaces are worn out, and the remains of cleaning products are completely burned out.
Features of cleaning two-stroke and four-stroke engines
The approach to maintenance depends on the type of engine. two-stroke Not only does the gas coar form in the cylinders, but it also forms on the exhaust windows, in the muffler and on the piston deflector, and the overgrowth of the exhaust windows reduces power because the cylinder purge is disrupted.
Cleaning a two-stroke often requires removing the muffler and exhaust stove, and these nodes can be completely clogged with a coke "coat." Burning or digestion in an alkaline solution are common methods for metal parts of the exhaust system.
In four-stroke engines, the main impact is on the valve group and the bottoms of the pistons. oil-capIf they're squandered from time to time, the oil will be continually fed into the combustion chamber, and no amount of cleaning will have a lasting effect without replacing the rubber bands.
The Myth of Adding Acetone to Fuel
There is a legend that adding acetone to gasoline cleans the engine. In practice, acetone is aggressive to rubber seals and plastic parts of the fuel system, which can lead to leaks and fire.
Also in four-strokes, it is important to monitor the crankcase ventilation system, a clogged PCV valve leads to an increase in crankcase gas pressure and an emission of oil into the intake, which speeds up coking.
Prevention and operational recommendations
The best way to control the pollution is to prevent it from forming, especially with regard to the quality of fuels. Use gasoline with the octane number recommended by the manufacturer, and quality synthetic or semi-synthetic oils with the right tolerance. JASO or API.
The mode of operation also plays a role. Long-term idle work (for example, while waiting for fish in the anchorage) is the main enemy of the engine. Periodically give the engine a load, putting the boat on plane, so that the temperature in the cylinders rises and there is a self-cleaning effect.
For two-stroke engines, use only fresh fuel mixtures. Oil gasoline has a limited shelf life (usually no more than 2-3 weeks), after which the oil precipitates and loses its lubricating properties, leading to increased soak.
Regular replacement of spark plugs and the use of fuel with detergent additives reduce the rate of soda formation by 30-40%.
Before putting the boat for winter storage, it is recommended to fill the fuel stabilizer and let the engine work for a few minutes so that the preservative compound gets into the carburetor or fuel ramp.
Can the engine be cleaned with water?
Water injection (water-methanol mixture) is used in tuning to reduce the combustion temperature and cleaning, but in regular outboard motors this can lead to corrosion and hydraulic shock.
How often should I do the decoding?
Preventive soft-coking can be done every 50-100 hours, aggressive cleaning with disassembly or strong chemistry - only when symptoms of rings appear.
Will the oil be used to help with the oil?
If the oil is caused by the rings being laid down by the soot, then the decoying can help restore mobility to the rings, and if the rings themselves or the valves' guide bushes are worn out, the chemistry will be useless.
Is it dangerous to get a scoop in the oil?
Yes, it's extremely dangerous. Aggressive chemistry destroys the structure of the oil, depriving it of its lubricating properties. After the decoking procedure, the oil and the filter must be replaced.