Owners of PVC boats and small boats often face a dilemma: power-drive Or take a model with a margin of safety, but with an underpower. The market offers many solutions where 98 cc engines (for example, the engine is not the same as the engine). Tohatsu or Mercury) artificially limited to 5 horsepower, this is done to allow for the possibility of driving without category “M” rights and simplified registration.
But when the boat is loaded with gear and passengers, the five forces are critically short for planing, and that's where the question of how to swell the unit safely and efficiently comes in, and it requires technical literacy, because the interference with the design changes the way it's designed. factory-likeness It can affect the engine life.
There are two main ways to solve the problem: mechanical intervention in the carburetor and software reprogramming of the ECU (for injector models). It is important to understand that any tuning removes the manufacturer's warranties. Before proceeding with modifications, you need to weigh all the pros and cons, and also evaluate your skills in working with the manufacturer. fine-mechanics.
Principles of operation of power limiters
Manufacturers use different methods to reduce the power of engines identical in volume. throttle-limiterIt could be a plastic sleeve, a propeller or a special washer that physically prevents the damper from opening to the full angle, and as a result, the engine cannot consume the maximum amount of fuel-air mixture.
In four-stroke motors, especially modern ones, there is often an electronic restriction. Control unit (ECU) It receives a throttle signal, but it software-shors the fuel supply or limits maximum speed, and in such cases, mechanical intervention is useless, requiring flashing or replacing the brains with a version for more power.
⚠️ Attention: Incorrect removal of mechanical limiters on some models can lead to depressurization of the carburetor or damage to the gas cable during a sharp jerk of the handle.
The third option is to use a smaller petal valve or change the timing phases, but this is rare for mass models of 5 hp Most often, engineers simply "strangle" the engine, leaving it the potential for upgrades. Understanding the type of your limiter is the first step to success.
Before starting work, be sure to find a service manual (Service Manual) for your model, as the design of carburetors in different years of release may differ.
Tools and training required
For quality engine modification You don't have to open the carburetor or remove the limiter on the knee without preparation, because you can lose small parts or damage the threads. Cleanliness and order in the workplace is the guarantee that the engine will work after assembly.
- 🛠️ A set of screwdrivers (cross and flat) of different sizes for carburetor screws.
- 🔧 Cover keys or heads for removing the covers and bolts of the casing.
- 🧼 Carb Cleaner and compressed air for purging channels.
- 🔩 Sealer for motors (usually gray or black) for the assembly of the body.
Particular attention should be paid to the state of spark plug If you plan to remove the restrictions, the ignition system will be under pressure, and an old candle with a large gap may not withstand the increased temperatures and stresses, leading to a potassium ignition.
It is also recommended to prepare a fuel drain tank and clean rags. Gasoline should not fall on plastic casing elements or rubber seals not designed for aggressive environments. Prepare a workplace with good lighting to see the marking of parts.
Mechanical scattering of carburetor motors
The most common method is to remove the mechanical limiter in the carburetor. Yamaha 5CMH or Tohatsu M5BDSThe limiter is a plastic sleeve inside the throttle or a screw resting on the throttle lever. Access often requires removing the top cover of the carburetor.
The process is this: once you have the carburetor dismantled and disassembled, you find a component that prevents the valve from running at full speed, and you need to carefully remove it or drill it without damaging the valve body, and then you put the unit back together in reverse sequence using a new one. gasketIf the old one is in disrepair.
☑️ Check after mechanical frothing
It's important to make sure that the gas cable goes all the way to the end and opens the valve completely, sometimes you need to adjust the tension of the cable or reposition the mount on the throttle lever. If after assembly the motor starts to work unstable, you may have broken the settings. idle.
⚠️ Warning: When removing the limiter, make sure that the throttle does not touch the walls of the diffuser. Metal contact with metal will lead to rapid wear and jamming of the engine on water.
Configuring the fuel mixture and chiclera
Simply removing the limiter is not enough. Increasing the volume of incoming air requires a corresponding increase in the fuel supply. If you do not do this, the mixture will become too poor, which will lead to overheating of the piston group and potential fuel supply. pistonCarburetor engines often require replacing the main fuel jellybar with a larger one.
The diameter of the new jeekler is selected experimentally or manually for an older model of the same family (for example, for 6 hp or 8 hp). A standard jeekler may have a marking, for example, #95, and for a blown version you will need #100 or #105. Mikuni carburettor or Keihin.
| Parameter | Standard (5bhp) | After a smothering (6-8 hp) | Risk of error |
|---|---|---|---|
| Head jeckel | Small diameter | Increased diameter | Poor mix, overheating |
| Air flap | Limited. | Full speed. | Tie break |
| Idle turn | 1000-1100 rpm | 1100-1200 rpm | It's dead on the water. |
| Mixture quality | Enriched | Normalized | Candle-stained garment |
The adjustment of the quality of the mixture is done by a screw located on the carburetor. As we twist it, we impoverish the mixture, twist it, enrich it. The optimal position is found by experimenting with the operation of the engine and checking the color. candle-plateThe perfect color is brick brown.
Electronic scattering of injection motors
Modern four-stroke motors, such as Tohatsu MFS5C or Mercury F5They often have an electronic injection system, and you can't do mechanical intervention. control unit (ECU)This requires a special diagnostic cable and software.
The process is to connect the laptop to the service connector of the engine and load a new fuel supply map and speed limits. There are off-the-shelf solutions from third-party developers that turn a 5-horsepower engine into a 6-horsepower engine in a software way, which saves engine life, because the changes are controlled.
Can I run the engine without the equipment?
Without the original dealer interface and licensed software, it's almost impossible to flash ECUs on your own, and trying to close the contacts can put the electronics out of order.
The advantage of electronic frothing is that it's reversible, and before you sell a boat or go through the maintenance, you can return the factory settings, but you have to consider that the dealership can see the history of the firmware in the error logs, which cancels the error. guarantee.
The impact of modification on resource and GIMS
Increasing power always leads to increased heat and mechanical stress, a 5 hp engine running at 8 hp will warm up more, which requires more careful control of the cooling system and quality. motor-oilThe intervals of oil replacement are better reduced by 20-30%.
From a legal point of view, an outboard motor with a capacity of more than 5 hp (or 3.68 kW) is subject to mandatory registration with the GIMS, and the driver must have the rights to drive a small vessel.
In the event of a water accident and subsequent examination, the interference with the structure will be revealed, which can lead to fines and problems with insurance companies, which will refuse to pay if the cause of the accident is a technical malfunction caused by a technical malfunction caused by the accident. topping up.
⚠️ Note: The use of a suffocated motor in waters with limited power (for example, in the city or in some recreation centers) may lead to the confiscation of the engine by the inspector.
However, for many anglers and tourists, the risk is justified by the possibility of confident glides with full load, the main thing is to perform the work efficiently and monitor the condition of the nodes.
Frequently Asked Questions (FAQ)
Will the engine life decrease after smothering?
Yes, the resource will decrease somewhat due to increased temperatures and rpm. However, with good maintenance and use of good oil, the difference will not be critical. 5 hp engines initially have a margin of safety, as they are based on blocks of 6-8 hp.
Can I return everything before selling?
In the case of mechanical friction, yes, if you have retained the removed parts (sleeves, washers, jellyplates); in the case of electronic flashing, yes, also by downloading the stock firmware; however, the opening marks of the seals may remain visible.
Which gasoline is best used after refining?
It is recommended to use gasoline with an octane number not lower than AI-95, and for forced modes and hot weather - AI-98. This will help to avoid detonation, which is harmful for the piston group.
Should I change the screw after a smothering?
Often, the regular rotor remains optimal, but if the engine does not reach the maximum recommended speeds (does not twist), it makes sense to reduce the pitch of the wing. If the speed exceeds the norm, the step should be increased so as not to “twistle” the engine.
The smothering of the 5 hp engine is a trade-off between usability and legal purity, and it's technically sound because the engine base allows you to develop more power.
In conclusion, the decision to modify is left to the owner, and if you have the technical skills and understand the risks, scattering will allow you to get a more comfortable and powerful machine for a reasonable price, the main thing is to remember about water safety and regular maintenance.