The issue of increasing the capacity of water transport is of concern to many owners of swimming facilities, especially those who have faced restrictions on the management of boats without appropriate rights. outboard motor frothing This is a technical procedure for removing factory restrictions, laid down by the manufacturer in the design of the unit. Most often, owners tend to turn 9.9 hp into a full 15-18 hp, getting a significant increase in speed and traction without buying a new engine.
But not all engines are equally upgradable. Some are designed to be safe at higher speeds, while others require major modifications or are not suitable for tuning. What outboard motors can be stirred upWe will consider the technical nuances of the process and assess the real risks associated with interference with the factory design.
It is worth noting that any interference with the engine removes it from the engine. warrantyIn addition, the increase in power entails a change in the class of the vessel, which requires re-registration in GIMS and the availability of the appropriate category of rights for the operator.
Technical aspects of power limitation in modern PLMs
Outboard motor manufacturers use several methods to artificially reduce power, and understanding these mechanisms is critical before any work is done. throttle-limiterIn carburetor models, this can be a physical stop or a washer that prevents the gas lever from opening the valve by 100%. In electronically controlled systems (EFI), the restriction can be software, although this is rare in the budget segment.
The second method is to change the timing phases or reduce the diameter of the carburetor's jellyclera, and a motor that runs on a lean mixture or with modified phases cannot physically produce full power even if the mechanical limiters are removed. Chinese manufacturers They often use simplified copies of cylinder heads from powerful models, simply changing the exhaust windows or installing another gasket.
⚠️ Attention: Removing the limiters on the engines with carburetors Mikuni or Keihin requires a mandatory adjustment of the mixture. If you just open the valve, but not replace the chicklers with more productive, the engine will run at the poverty limit, which will lead to overheating of the piston group and possible bullying.
The third aspect is the throughput of the exhaust system and the cooling system, and the 15 hp engine produces more heat and exhaust gas than the 9.9 hp version, and if the cooling system is not designed to be loaded, the engine will be more efficient. thermostat It can be a failure, and a water pump can be a failure, which is why it's important to know which model is at the heart of your low-power aggregation.
Popular models of Chinese engines for fragrance
The market is saturated with Chinese copies of well-known Japanese brands, most of which are based on the time-tested designs of Yamaha and Tohatsu, making them excellent candidates for tuning. HideaThe HD-A series (a copy of Yamaha A) and HD-F (a copy of Yamaha F) have almost identical cylinder block designs.
Motors. Parsun and HDX They are also often built on Tohatsu engines, and their advantage is that parts and manuals from the original Japanese counterparts fit them 95% of the time, making it easier to find out exactly how a particular model is scattered. For example, the popular 9.9 hp often turns into 15 or 18 hp by simply replacing the gasket under the cylinder block and removing the limiter on the carburetor.
- 🚤 Hidea HD9.9FHS - A full copy of the Yamaha 9.9F, swelled to 15 hp by replacing the gasket GBC and adjusting the carburetor.
- 🚤 Parsun F9.9BMS - analogue Tohatsu M9.9, requires replacement of petal valves and jellyplates for a safe exit of 18 hp.
- 🚤 HDX T 9.9 BMS - structurally similar to Yamaha, often enough to remove the plastic emphasis on the throttle lever.
- 🚤 Sea-Pro F 9.9S - a copy of the old Yamaha two-stroke, easily upgradeable to 15 hp
It is important to understand that compression The Chinese engine cylinders may be lower than the original ones because of the surface treatment quality, so it is recommended to measure the compression before blowing, and if it is significantly lower than normal, increasing the power will only accelerate the wear of the engine.
Japanese Classics: Yamaha and Tohatsu
Japanese engineers have created a benchmark of reliability that the Chinese have been copying for decades. Yamaha 9.9 GMHS and Tohatsu M9.9B These are essentially the same 15-horsepower units, but with limitations. In two-stroke versions, the difference is often the size of the exhaust windows and the configuration of the carburetor. Four-stroke versions differ in the firmware of the CDI module or the physical restriction of the throttle.
For two-stroke Yamaha In the classic series, the process often boils down to squandering the exhaust windows in the cylinder (if they are understated) and replacing the carburetor or jellyplates. However, modern four-stroke models of the F series can have a more complex system of restraint. Sometimes you need to solder resistors in the control unit or use special programmers, although in the mass segment 9.9-15 hp mechanical methods still prevail.
The system deserves special attention. gas-distributionSome Tohatsu models have a valve with a smaller stroke or a modified camshaft for the 9.9 hp, in which case simply replacing the GHC gasket will not have the full effect, and the engine will run inefficiently, using more fuel per unit of power.
CDI's secret codes
Some Yamaha CDI units have hidden modes activated by closing certain contacts in the diagnostic connector. However, in civilian versions of 9.9 hp this is rare, most often the restriction is purely mechanical.
American and European brands: Mercury and Evinrude
Motors. Mercury They're often twins of licensed Tohatsu models, so their scenting is almost identical to that of Japanese models, and if you have a Mercury 9.9 hp, you probably have a Tohatsu engine under the casing, and you need to look for instructions for that brand, which makes it easier to find parts and supplies.
The situation Evinrude and Johnson These motors often have unique injection and control systems, and scattering these units requires electronics interventions that are virtually impossible or economically impossible without specialized equipment and software, and mechanical intervention attempts can disrupt the lubrication system, which is critical for two-stroke E-TECs.
For owners. Mercury carburetor (the good news is) they often have standard Mikuni carburetors, and replacing GMain Jet with higher bandwidth numbers allows you to safely raise power if you remove the throttle limiter, and it's important to find the right spark plug, because the heat number must match the increased loads.
Step by step: Mechanical scattering of the carburetor motor
Consider the process using a typical four-stroke 9.9 hp engine, which is a copy of Yamaha. The process requires accuracy and a basic set of tools. Before starting work, make sure you have a new gasket under the cylinder head (GBC) and, preferably, a set of chicks for the carburetor.
First you have to dismantle the fuel system and remove the carburetor, find the throttle limiter screw, it can look like a regular adjusting screw with a plastic plug or a stop, removing this stop allows the gas lever to open the valve by 100%, but if you don't enrich the mixture, the engine will start to "gap" at high speeds.
☑️ Checklist before launch after smothering
The second step is to work with the head of the block. Remove the GBC and inspect the gasket. In the 9.9 hp stock version, it can have a jumper that covers the part of the exhaust window, or be simply thinner / thicker than you need. Replacing the gasket with the 15-strong version (or its modification) opens the exhaust gasket full way. It is also worth checking the petal valves for gaps.
| Parameter | Stock version (9.9 hp) | After suffocation (15bhp) | Recommended value |
|---|---|---|---|
| Head jeckel | #90 - #95 | #105 - #110 | Picks up by the color of the candle |
| Candle gap | 0.9. 1.0 mm | 0.8. - 0.9 mm | 0.85 mm |
| Thermostat temperature | Opening 50°C | Opening 50°C | No change. |
| Max. Turnover. | 5000-5500 rpm | 5500-6000 rpm | According to manual |
After the assembly must be carried out break-in Or at least a thorough water test, the first 10 minutes of operation should be at a speed of 50 percent or less, watch the engine temperature and the water pump jet, and if the temperature is rising too fast, the cooling system may not be able to cope with the increased heat load.
When swelling a two-stroke engine, be sure to use high-quality oil (JASO FD or TC-W3) in a ratio of 1:50, even if the manufacturer allowed 1:100.
Electronic smothering and work with CDI modules
In modern motors, especially with EFI or electronic ignition, the key element is the CDI (Capacitor Discharge Ignition) unit, which controls the ignition angle and maximum speed. Some craftsmen offer soldering resistors inside the CDI or the use of sports modules.
However, on most budget four-stroke engines with a capacity of up to 20 hp, there is no electronic power limitationThe restriction here is mechanically implemented through the carburetor and the gasket of the GHB. Trying to get into electronics on these models is a waste of time and money. The electronics in them are only used to form the spark and work the ignition coil.
If you have a fuel injection engine, it's different, it's software-constrained, it requires ECU (Engine Control Unit) flashing to remove the limits, a complex procedure that requires a special interface and software that is often only available to authorized dealers, and self-flashing threatens to turn the engine into a brick.
⚠️ Attention: Interference with the electronic engine control system (ECU/CDI) can lead to irreversible failure of expensive components, warranty on such engines is lost instantly, and factory resetting without a dealer scanner may be impossible.
Legal consequences and risks of exploitation
Before starting technical work, you need to understand the legal side of the issue. According to Russian legislation, engines with a capacity of more than 10 hp (8 kW) require registration of the vessel and the right to operate a small vessel of the appropriate category. By swelling the engine from 9.9 to 15 hp, you formally violate the rules of operation.
If the documents are checked by the inspector of the GIMS, the technical examination will easily reveal the interference with the design, this threatens not only with a fine, but also with the confiscation of the vehicle. In addition, in the event of an accident or an accident on the water, the fact of illegal modification of the engine will become an aggravating circumstance and can lead to the refusal of the insurance company in payment.
Technical risks are also high, the resource of the engine, operating with increased load, decreases fuel consumption, increases the likelihood of overheating and failure of the piston group. junction-piston is experiencing heavy loads, which can lead to a rod break and the destruction of the engine on the go, which creates a dangerous situation on the water.
The frothing of the engine is always a compromise between the desired power and the resource of the engine. It is safer to buy an engine that is initially more powerful than to force a weak one.
Frequently Asked Questions (FAQ)
Will the engine life decrease after the smothering?
Yes, it's guaranteed to be depleted. The engine will run at higher temperatures and loads. If the stock engine runs 1,000 hours, the suffocated engine can go 500-600 hours in active use. The build and oil quality is key here.
Can the engine be suffocated if necessary?
In most cases, yes. If you have retained all the parts removed (pads, washers, limiters), the process is reversible. However, the autoburettor's gaskets and adjusting screws will remain open, and the service center may refuse warranty repairs even if you returned it as it was.
Will fuel consumption increase after the increase in power?
Yes, fuel consumption will increase in proportion to the increase in power and rpm. The 15 hp engine consumes about 20-30% more fuel than the 9.9 hp version when operating at full speeds. At cruising speeds, the difference may be less noticeable, but it will.
Which octane of gasoline is best used after scenting?
It is recommended to use gasoline with an octane number specified in the instructions for the full version of the engine (usually AI-95). Using low-octane fuel on a forced engine can cause detonation that will destroy the pistons and valves very quickly.