The operation of the outboard motor, whether it is a powerful Yamaha compact MercuryNagar is solid deposits of carbon, resins and unburned oil particles that settle on the walls of the combustion chamber, pistons and valve bottoms, and ignoring this problem can lead to reduced compression, potassium ignition and even bullying in cylinders, which will require expensive overhauls.
Timely cleaning allows you to restore the passport power and reduce fuel consumption. There are two main approaches to this problem: the chemical method (disassembly) without disassembling the engine and mechanical, requiring the dismantling of the cylinder head. outboard.
In this article, we will discuss both methods in detail, evaluate the effectiveness of various liquids for decoking and give professional recommendations for prevention. It is important to understand that the process of decoction requires care, since aggressive chemistry and mechanical action can damage parts if not followed by technology.
Causes of formation and symptoms of pollution
The main reason for the appearance of abundant soda is the use of low-quality fuel or the imbalance in the mixing of gasoline and oil in two-stroke engines. If the mixture is too fat (a lot of oil), it does not have time to burn completely and settles in the form of a sticky plaque, which then turns into a hard crust, also contributes to the formation of sediments long-term work at idle speeds, or, conversely, constant work at maximum speeds without periodic cleaning.
There are a number of telltale signs that you can tell if you're critically polluted, and you start losing traction, you get worse at opening the throttle, and you have some problems starting, especially when you're hot, because you're going down. compression and heat sink disturbances.
- 🔥 The appearance of detonation (sound knocking when working under load) due to red-hot particles of loot.
- 💨 Increased exhaust smoke and change in the color of the exhaust gases.
- 📉 A marked drop in the boat's maximum speed at full gas.
Another worrying symptom is that the engine is overheated, even if the cooling system is in good condition, and the coarse layer is thermally insulating, which causes the heat to be lost to the piston and cylinder head, which creates a risk of piston burnout, and if you notice at least two of these signs, the cleaning procedure becomes necessary.
Preparation for the decoking procedure
Before starting work, you need to prepare the workspace and tools. The chemical method is the most popular, because it does not require a complete disassembly of the engine. Lavr, Hi-Gear or Shumakoff), a set of candle keys, a syringe with a tube and, preferably, a purging compressor.
However, before the introduction of aggressive chemistry, you should make sure that the ignition system is serviceable, since after the procedure, the candle will most likely have to be replaced or thoroughly cleaned.
Safety is paramount. Work should be done in a well-ventilated area or outdoors, away from fire sources, solvent vapors are toxic and flammable, and prepare a container for waste oil if you plan to change it immediately after the procedure, which is a mandatory step.
Chemical method: step-by-step instructions
The method is to pour the cleaning compound directly into the cylinders through candle holes, allowing the solvent to soften the soak on the piston rings and cylinder walls. First warm the engine to operating temperature, then shut it down.
Unscrew all spark plugs. Through the holes, check the condition of the cylinders visually (if possible) or by touch (carefully). Next, you need to set the pistons in the middle position so that the liquid washes the rings on all sides. In each cylinder, pour the recommended amount of product (usually 30-50 ml) through a syringe.
☑️ Checklist before chemistry launch
Roll the candles back (you can use old ones, not too bad) or simply plug the holes with rags to create pressure and prevent evaporation. Leave the engine to oxidize for the time specified in the instructions (usually from 1 to 12 hours). Periodically, every 30 minutes, it is recommended to turn the crankshaft with a starter (with twisted candles or in scrolling mode) so that the liquid penetrates deeper.
⚠️ Warning: Once exposure time is over, be sure to unscrew the candles and swivel the engine with a starter several times (no candles!) to knock out the remnants of solvent and softened soda from the cylinders. If you don't, a hydraulic shock may occur at start that can bend the rods.
The final step is to screw in new or cleaned candles, start the engine and work at variable speeds for 10-15 minutes, after which you need to completely replace the engine oil and oil filter (for four-stroke engines), as some of the chemistry will inevitably get into the crankcase.
Mechanical cleaning and defective
If the chemistry didn't work, or if the soda was baked into a hard crust (coke), it would require mechanical cleaning, which involves removing the cylinder head, and it's more time-consuming, but it allows you to visually assess the condition. valve, saddle and pistons.
The cleaning uses soft metal brushes, scrapers (soft metal to avoid scratching aluminum) and special carburetor aerosols. The piston bottom and combustion chamber are removed carefully, without excessive effort. Special attention should be paid to piston rings: they should move freely in grooves.
Do I need to polish the valve?
Yes, if they have shells or heavy loading that prevents the plate from fitting tightly to the saddle, but the polishing is done only with laundry paste, and after the procedure, it is mandatory to check the tightness with kerosene.
After mechanical cleaning, all surfaces are thoroughly degreased and blown with compressed air, and assembly is done with new HBC gaskets, a method often combined with the replacement of valve ossicles if the engine is four-stroke, because access to them is already open.
Comparison of engine cleaning methods
The choice between chemistry and mechanics often depends on the budget and skills of the owner, and here is a comparison table to help you decide on the method.
| Parameter | Chemical decoking | Mechanical cleaning |
|---|---|---|
| Complexity | Low (available to beginners) | High (requires skills) |
| Time spent | 2-12 hours (mostly waiting) | 4-8 hours of active work |
| Efficiency | Medium (for prevention) | High (removes hard coke) |
| Risk of damage | Minimum | Medium (scratches, assembly errors) |
The chemical method is ideal for regular maintenance every 50-100 hours. The mechanical method is the "heavy artillery" for motors with mileage or obvious symptoms of rings, ideally these methods can be combined: first try the chemistry, and if the result is unsatisfactory, move to disassembly.
Prevention and maintenance of the engine
The best way to control the pollution is to prevent it from forming in critical volumes. Use only quality fuel with an octane number recommended by the manufacturer (usually AI-92 or AI-95). TC-W3 and observe the proportions of the mixture.
Use fuel cleaners regularly by adding them to the tank. They work softer than decoking, but when used continuously prevent resinous deposits from forming.
The operating style also affects the purity of the engine: periodically let the engine run at high speeds (in safe mode) so that the temperature regime promotes self-cleaning of the combustion chamber. Prolonged operation of the "traction" at low speeds, on the contrary, contributes to coking.
Change spark plugs regularly. Candle soak is a great diagnostic tool. If the candle is black and dry, it's rich, if the white is poor, if it's in red, maybe there's ferrocene additives in the fuel that you should avoid.
Frequently Asked Questions (FAQ)
Can acetone or solvent be used instead of special chemistry?
You can use technical solvents, but with caution, as they can aggressively affect rubber seals. Acetone is too aggressive and evaporates quickly, which reduces efficiency. Specialized means (Acetone is too aggressive and evaporates quickly).Lavr, Greenol) contain lubricating additives to protect the piston-cylinder group during the process.
How many times a season do you need to do the decoding?
For actively operated outboard motor, preventive decoking is recommended 1-2 times per season or every 50-70 motor hours. If the engine is new, the first procedure can be carried out after running.
Will the engine be able to use oil if the engine is already using oil?
If the oil is caused by piston rings being deposited due to the swelling, then the decoying can help and restore mobility to the rings, but if there is mechanical wear of the cylinders or damage to the osteoils, the chemistry will be powerless - repair will be required.
Is it dangerous to get a decoker into the cooling system?
With the right procedure (through candle holes) you can't get into the cooling system, because these are different circuits. The danger is that a lot of chemicals get into the oil, so changing the oil after the procedure is mandatory.
Do I need to warm up the engine after cleaning?
Yes, after the procedure, you need to let the engine work at idle speeds for 10-15 minutes, and then drive (swim) several kilometers in a gentle mode, this is necessary to burn out the residue of chemistry and stabilize the engine.