Choosing an outboard motor for a small inflatable or aluminum boat often turns into finding the perfect balance between cost, weight and traction. The market is oversupplied, but there are models that can surprise even experienced water-engineers with their versatility. Mikatsu M9.9BMSThe engine is technically a 9.9-horsepower unit, but it hides the potential of a much more powerful engine.
This engine became a real hit due to the possibility of software and technical processing in 18 horsepower without replacing the main components of the cylinder-piston group. Two-stroke circuit The work provides excellent throttling, and the availability of electronic ignition CDI makes the power plant stable at all speeds, and owners value this model for its ease of maintenance and availability of spare parts, which is critical for long trips to the water away from service centers.
In this article, we will discuss in detail the design features, the actual fuel consumption, the nuances of power transformation and the typical problems you will encounter during operation, you will learn why this engine is often called “people’s” and how to properly run it in order to serve for many years.
Technical specifications and design features
At the heart of the unit is a two-cylinder engine with a displacement of 246 cubic centimeters. Despite its compact size, it is able to accelerate a boat up to 4 meters long with a full load before planing. The lubrication system works on the principle of mixing gasoline with oil, which requires the owner to strictly observe the proportions, especially during the primary break-in.
The ignition system is built on the basis electronic module CDIIt's a lightweight, corrosion-resistant body that provides a powerful spark even at low crankshaft speeds, making it much easier to start the engine in the cold season, and it's made of lightweight alloys that are corrosion-resistant, allowing the motor to be used in both fresh and salt water without the risk of rapid corrosion.
An important feature is the presence of a forced water cooling system with a control trickle, which allows you to visually evaluate the pump during movement, if the trickle disappears, you need to immediately shut down the engine to avoid overheating and jamming pistons.
⚠️ Warning: Before each start, be sure to check for water in the control hole. Operating the engine without water cooling for even 10-15 seconds can lead to irreversible damage to cylinders and piston rings.
The weight of the engine in running order is about 36 kilograms. This is enough for a formally "nine", but it is quite justified for a model that is structurally ready to produce 18 forces. transom clip allows you to quickly install and remove the unit, and the tiller control gives you full control over maneuvers.
Power Transformation: from 9.9 to 18 hp
The main feature of this model is the ability to increase power. The manufacturer initially designs a cylinder-piston group with a margin of safety that allows you to shoot up to 18 horsepower. However, at the exit of the conveyor, the power is artificially limited by a programmatic and structural throttle.
A number of mechanical actions are required to unlock the full potential, primarily the replacement or modification of the throttle in the carburetor, which physically restricts the passage of the gas cable, and often requires replacing the petal valve with a more productive one and installing another exhaust system or laying additional channels to drain gases.
What does CDI flashing give?
Replacing or flashing the CDI unit removes the electronic speed limit. Without this step, even with a fully open valve, the engine will not reach maximum power, since the spark will be supplied with a delay, limiting the maximum rotation of the crankshaft.
After mechanical modification, you need to reflash or replace the block CDIIt's where the ignition cards are stitched up, which prevent the engine from spinning above a certain limit, and then the engine behaves like a full 18-strong engine, increasing the top speed, improving the sleeve output with heavy loads.
Keep in mind that increased power leads to higher demands on fuel and oil quality, and the heat load on the engine increases, so the intervals for changing the candle and checking the cooling system should be reduced.
The 18 hp conversion of the Mikatsu 9.9 is a standard procedure popular with water-engineers, but it requires precision in setting up the carburetor to avoid overheating.
Fuel consumption and efficiency of operation
Two-stroke engines are traditionally considered more "gluttonous" compared to four-stroke counterparts, but modern technology has minimized this gap. Mikatsu 9.9 It depends on the mode of operation, the weight of the boat and the condition of the propeller.
In quiet trolling or low-speed (about 3000 rpm), the engine consumes about 2.5-3 liters of fuel mixture per hour. When going into planing and driving at full speed, the flow can reach 4.5-5 liters per hour.
- 🛶 At a speed of 20 km / h, the flow rate will be about 2.8 liters per hour.
- 🚤 At full planing (about 35-40 km / h), consumption grows to 4.5-5 liters.
- ⛽ The use of high-quality oil in a ratio of 1:50 reduces nagaroformation and stabilizes consumption.
And it's important to note that the economy is very much dependent on the carburetor being set up correctly, and if the mixture is too rich, some of the fuel will just fly into the exhaust pipe, staining the water into colored spots and reducing traction, and the poor mixture, on the contrary, is dangerous to overheat.
To save fuel on long transitions, try to keep the speed in the range of 80-85% of the maximum. This is the zone of the most efficient combustion of the mixture for two-stroke engines in this class.
Season preparation and breaking in procedure
Proper running is the key to a long life for your engine, and many owners ignore this step, relying on factory training, but grinding the parts of the cylinder-piston group in the home or on the water is critical. The new engine cannot be immediately loaded to full capacity.
The break-in process takes about 10 hours, and the first hours should be spent at idle and low speed, gradually increasing the load, which allows the piston rings to press evenly against the walls of the cylinder, ensuring the necessary tightness.
☑️ Checklist of Mikatsu 9.9 break-in
During the break-in, the ratio of mixing of gasoline and oil must be strictly observed. 1:25 for the first tanks, even if the instructions allow 1:50The increased oil fraction will create a more reliable film on rubbing parts. After the first 10 hours of motoring, be sure to replace the fuel filter and check for tightening of all bolt joints, as vibration may weaken them.
⚠️ Warning: Never keep the engine at full speed all the time during the first 10 hours of operation. The mode of operation should be variable: acceleration - movement - deceleration. This will ensure that all engine modes are uniformly laden.
Comparison with competitors and the specifications table
In the outboard market, the Mikatsu 9.9 has direct competitors such as Hidea, Sea-Pro and Tohatsu. Mikatsu’s main advantage often lies in a more affordable price with similar or even better performance after refinement. Many nodes are unified with popular Japanese models, making it easier to find spare parts.
Consider the comparative specifications of the Mikatsu 9.9 with a conditional average competitor in the 9.9-15 hp class:
| Parameter | Mikatsu M9.9BMS | Average competitor | Unit of measurement |
|---|---|---|---|
| Workload | 246 | 240-250 | cm3 |
| Max. power (after completion) | 18 | 15 | hp |
| Weight. | 36 | 34-38 | kilogram |
| Ignition system | CDI | CDI / TCI | - |
| Recommended oil | TC-W3 | TC-W3 | - |
As you can see from the table, Mikatsu It offers a larger margin of power after the upgrade, but the weight of the motor can be slightly higher because of the use of more massive materials in lower unit to ensure reliability. For inflatable boats, this is not critical, but for lightweight aluminum flat-bottoms, every kilogram per transom makes a difference.
In terms of maintenance, the engine also beats many nouneime brands: the carburetor design allows cleaning and adjustment without special equipment, and access to candles and thermostat does not require complete disassembly of the engine.
Typical malfunctions and their elimination
Despite the reliability, there may be problems in operation, most often fuel quality or operating irregularities, and knowing the underlying symptoms can help quickly diagnose a water malfunction.
One of the common problems is unstable idling or spontaneous engine stop, often caused by clogging of carburetor jelly or the presence of water in the fuel, and it is also worth checking the state of the spark plug: black increments indicate a rich mixture, and white - poor or overheating.
Another common situation is overheating, and if the control trickle has become weak or gone, it may have been mud, algae, or impeller pumps that have collapsed, and then you need to remove the lower unit and clear the cooling channels.
⚠️ Attention: If you experience a knock or a sudden loss of power, do not try to "add gas" to get to the base. This can lead to a twist of the liners or bullying in the cylinders, it is better to eliminate the cause on the spot or cause evacuation.
To prevent problems with the fuel system, it is recommended to use a fuel filter-sludge tank and regularly change it. Cheap gasoline from unknown gas stations may contain impurities that quickly disable the sensitive channels of the carburetor.
Frequently Asked Questions (FAQ)
Can I use the Mikatsu 9.9 with a high-strength screw?
Yes, a propeller with increased pitch (for example, 11-12 inches instead of the standard 9-10) will increase the maximum speed on light boats. However, when fully loaded, the engine may not have enough traction to confidently exit into planing, and it will operate in overload mode.
Which oil is better to put in the fuel mixture?
Only high-quality mineral or semi-synthetic oils for two-stroke engines with labeling must be used. TC-W3The use of motorcycle or trimmer oils (JASO FB/FC) is unacceptable, as they form more soda and can clog the muffler.
Do I need to drain water from the engine for the winter?
After operating in salt water, the motor should be washed with fresh water, and when stored, it is recommended to blow out the compressed air cooling system or use a special anticores to prevent residual moisture from corrosive internal channels when frozen.
Is it really possible to accelerate a boat to 40 km / h with this engine?
Yes, it is, but only after the transformation of 18 hp and using a light inflatable boat (PVC) length of 3.2-3.6 meters with one passenger. On heavier boats or with two passengers, the speed will be lower, in the area of 30-35 km / h.