Choosing a power unit for a small vessel often becomes a compromise between the desired speed, weight of the structure and the cost of equipment. Mikatsu 9.9bhp. It is one of the leading companies in the Russian market, offering the best combination of Japanese technology and affordable prices, and has long been a reliable working option for fishermen and water enthusiasts.
The popularity of the model is explained not only by the manufacturer's pricing policy, but also by the high maintenanceability of the units. The owner receives an engine that is able to confidently display heavy PVC boats or small metal boats for planing. Mikatsu allows you to significantly extend the life of the engine and avoid typical errors during operation.
In this article, we will discuss in detail the technical details, the process of running and the finer details of setting up the power system. You will learn why this engine is often called “unkillable” with proper care and how to unleash its potential 100%.
Technical specifications and design features
Engine. Mikatsu M9.9BMS It is based on the time-tested architecture of the Tohatsu two-stroke motors, which ensures a high degree of unification of parts and ease of maintenance. The cylinder capacity is 169 cubic centimeters, which is the standard for the 9.9-strong class. The ignition system here is electronic (CDI), which guarantees stable start-up in all weather conditions without the need to constantly change candles.
The cooling system deserves special attention, and it belongs to the type of forced water, where water is drawn through holes in the lower unit. impeller It's made of wear-resistant rubber, but it's extremely sensitive to dry work, and the design of lower unit is designed to have an anti-cavitational stove that improves fluid dynamics and protects the propeller from impacts on floating objects.
The dry weight of the engine is about 26 kilograms. For a two-stroke model, it is an excellent indicator that allows you to easily move the unit alone. Transportation is possible in any position thanks to the oil lubrication system mixed with gasoline, which eliminates the risk of oil starvation when rolling. Mikuni carburetor type provides accurate dosing of the fuel mixture.
⚠️ Attention: Never start the engine out of water or without a pre-connected external water system. The pump "dry" leads to instant melting of the impeller and overheating of the lower unit, which is not a guarantee case.
Let’s look at the main parameters in the summary table for ease of comparison:
| Parameter | Meaning |
|---|---|
| Type of engine | two-stroke, 2-cylinder |
| Workload | 169 cm |
| Maximum power | 9.9bhp at 5,500 rpm |
| Ignition system | Electronic CDI |
| Weight (no fuel) | 26 kg |
The crankcase is made of lightweight aluminum alloys with anti-corrosion coating, which is critical for use in salt water or in aggressive environments. lower unit It has an elongated leg, which allows the motor to be used on boats with high transes, and all fasteners are made of stainless steel, which minimizes the risk of rust even after a long season.
The process of proper running of the new engine
The first hours of operation determine the entire further life cycle of the mechanism. Mikatsu 9.9 It requires strict adherence to the proportions of the fuel mixture and time intervals, and unlike modern four-strokes, the process of grinding the piston group is more intense because of the peculiarities of oil lubrication.
To prepare the mixture, you need to use a high-quality two-stroke oil with marking TC-W3The ratio for the break-in period should be 1:25 (40 ml of oil per 1 liter of gasoline). After the first tanks are developed (usually 10 motor hours), the mixture can be switched to the standard 1:50. It is recommended to use AI-92 or AI-95 gasoline from tested gas stations, avoiding fuel with an expired shelf life.
The process of running in is divided into several stages in terms of operating time at different turns. You can not immediately give full gas. The first 10 minutes of the engine should be idling, then the cycle of operation at low and medium speeds. Only after 2-3 hours of operation, a short-term opening of the throttle valve by 80% is allowed.
☑️ Checklist for break-in preparation
When running, watch the temperature of the body carefully. If the hand barely tolerates touching lower unit, this is normal, but if the metal begins to turn blue or you smell burnt, immediately turn off the engine. Temperature conditions It's also important to check the control jet periodically, which should be flat and pulsating.
Setup of the carburetor and power system
Factory setting of the carburetor Mikatsu However, when operating at high altitudes, with a non-standard screw or after a long winter, adjustment may be required. The carburetor has two main screws: an idling screw and a mixture quality screw (L).
Adjustment is done on a warm engine, first, the idle screw achieves stable operation without deafening, then carefully adjust the quality screw, achieving maximum idling speed, and then enrich the mixture a little. Poor mix. dangerous overheating piston, and rich - soak on candles and loss of power.
⚠️ Attention: Do not try to twist the screws adjustment more than 1.5-2 revolutions from the factory position. This can disrupt the balance of air flow and lead to unstable operation of the engine in all modes.
Clean fuel system is the key to a long life of the engine. Be sure to use a fuel filter-sludge, which is often included or purchased separately. Water in gasoline is the main enemy of the two-stroke engine, causing corrosion of the carburetor and bullies in the cylinders. Regularly drain the suck from the transparent filter bulb.
Symptoms of improper tuning of the carburetor
If the spark plug is covered with black velvety soda, the mixture is too rich (a lot of oil or little air). If the electrodes are white or melted, the mixture is poor (a little oil or a lot of air), both require adjustment of the needle or chiclera position.
To accurately diagnose the condition of the mixture, you can use a special thermocouple sensor installed under a candle. The optimal combustion temperature in the cylinder should be within the range specified by the manufacturer. carburetorIt is better to entrust this procedure to a specialist of the service center.
Selection of screws and the impact on the speed of the boat
The speed and efficiency of the boat depend on a properly selected propeller. Mikatsu 9.9 It's a common 9-10 inch propeller, a versatile option for heavy inflatable boats with 2-3 passengers, but for light PVC or single-driver metal boats, this can be a big step.
If the motor doesn't get on plane or growling, but it doesn't accelerate, the pitch is too high. The engine is running in overload mode without gaining the required 5000-5500 rpm. In this case, you need to reduce the pitch of the screw. And vice versa, if the engine "shows" gaining 6000+ rpm, but the speed is not growing - the step is small, and the engine runs in spasm.
- 🚤 For heavy PVC boats (330-360 cm) with a load, a propeller with a pitch of 9-10 inches is optimal.
- ⚡ For light boats and fishing alone, a screw with 8 inches increments is better.
- 🛥️ Flat-bottomed metal boats often require propellers with reinforced construction and 10-11 inches in pitch.
The material of the screw also matters. Aluminum screws are cheaper and lighter, but when hit by a stone they bend, which saves the gearbox from breaking. Stainless steel is stronger and gives a speed gain of 3-5%, but when hit hard can transfer the load to the lower unit. aluminum screw It is a safer choice from a financial point of view.
When changing the screw, always use a new veneer and make sure the nut is tightened at the right moment. The self-contradicting nut requires replacement after each removal. Checking the screw condition should be regular: the presence of chips, cracks or deformation of the blades leads to vibration and destruction of the lower unit bearings.
Maintenance and winter storage
Regular maintenance avoids costly repairs: every 50 hours or at the end of the season, a complete revision is required, and first of all, the gearbox, which has to be changed annually, regardless of the mileage, and the condensation that gets inside through the glands turns into an emulsion (mayonnaise) that kills the gears.
All friction nodes (gas cable, pivot hinges) must be lubricated with special marine lubricants that are not washed away with water. Lithium-containing lubricants are washed out quickly, so their use in lower unit is unacceptable. Bearings lower unit require professional replacement when backlash or noise, as their wear leads to the destruction of the osteoils and water entering the engine.
In preparation for winter storage, the engine must be preserved, so that a small amount of engine oil is poured into the cylinders through the candle holes and the starter (or the cord) is scrolled to ensure that the oil covers the cylinder walls, which will prevent corrosion during downtime.
Keep the motor upright only. Bending or storing on the side can lead to oil leaking into the crankcase and the crankshaft glands drying out, causing startup problems next season.
Ignition plugs are consumables. Even if they look normal, they are recommended to be changed every two seasons or cleaned with ultrasound. The sugar on the electrodes worsens spark formation, especially when starting a cold engine. Always keep a set of new NGK or Denso candles that correspond to the kalyl number specified in the manual.
Typical malfunctions and methods of their elimination
Despite the reliability, Mikatsu 9.9 You can run into a number of typical problems, most often owners complain about difficulties starting. If the engine doesn't start, the first thing you do is check for sparks and fuel supply. Often the problem is with contaminated carburetor jelly or old gasoline, which has lost its properties in a month of downtime.
The second common problem is overheating. In addition to running without water, the cause can be a clogged water intake (grass, sand) or the destruction of the impeller pump. If the control jet becomes weak or disappears, immediately stop operation. It is also worth checking the thermostat if it is structurally provided in your modification, although 9.9 hp it is often not, and the cooling is straight-flowing.
- 🔥 Shoots at the silencer: Distribution phases are disrupted (rarely) or a mixture that is too rich.
- 💨 Smokes with blue smoke: It is normal for a two-stroke, but if the smoke is black, the oil burns.
- 🔊 Knocking in lower unit: wear of bearings or rod liners, urgent repair is required.
⚠️ Attention: If you experience a knock or a sharp loss of power, do not try to reach the shore on full gas. This can lead to bullying piston group and expensive overhaul of the engine.
Diagnostics of compression helps to assess the general condition of the cylinder piston group. Normal compression for this engine should be in the area of 8-10 atmospheres. The spread of values between cylinders of more than 1 atmosphere indicates problems with tightness (seals, gaskets) or wear of the rings.
Timely replacement of fuel filters and use of high-quality mixture prolong life of carburetor and piston group by 2-3 times, saving considerable money on repair.
Frequently Asked Questions (FAQ)
What is the best oil to use into the Mikatsu 9.9 gearbox?
Use only special transmission oil for outboard motors with the marking GL-5 or specification API GL-5It has the necessary anti-sharp properties and emulsification resistance, and conventional car oil will quickly lose its properties in water-cooled conditions.
Can I fill up Mikatsu with 9.9 AI-92 gasoline?
Yes, the engine runs perfectly on AI-92 gasoline. The AI-95 is acceptable, but it does not give a significant increase in power, but only slightly reduces the risk of detonation under high loads. The main thing is the freshness of the fuel and the absence of ethanol impurities, which destroys the rubber elements of the carburetor.
What is the real maximum speed with this engine?
Speed depends on the boat and the load. A light PVC boat with one person can develop 30-35 km / h. A heavy boat with three passengers and a cargo will go at a speed of 15-20 km / h. planing is a key parameter, and here Mikatsu 9.9 shows excellent results for its class.
Do I need to disassemble the engine after each break-in?
No, no major disassembly after the first break-in is required, just change the oil in the gearbox, check the tightening of the diewood mounting bolts and exhaust system, and clean the candle, further maintenance is carried out according to the regulations (every 50-100 motor hours).