Choosing a powered motor for a lightweight inflatable boat or a small catamaran always involves finding the perfect balance between weight, power and reliability. In the low-power segment, often called the “tretch”, the undisputed market leader for decades remains the undisputed leader in the market. Japanese brand YamahaMany aquatic motorists are still looking for information on the request "outboard motor yamaha 3 liters with specifications", as this model has become a kind of classic, a benchmark against which all other engines of this class are compared.
The two-stroke 49 cubic centimeter design provides excellent low-speed traction, which is critical for planing under full load. Despite the emergence of many Chinese counterparts and the industry's transition to four-stroke technology, the company said in a statement. Yamaha 2CMHS The model (the official name of the model) retains its popularity due to the phenomenal repairability and availability of spare parts in any service center.
In this article, we will take a look at all the technical details, the actual consumption of the fuel mixture and the hidden features of operation, which are often silent sellers, you will learn why this engine weighing only 9.8 kg is able to to tow a boat with two adult passengers and how to properly run it so that it will last for decades.
Technical specifications and design features
The basis of the reliability of this unit is a time-tested two-stroke circuit with loop blowing cylinders. The displacement of 49 cm3 seems negligible, but engineers managed to remove 3 horsepower from it at 5500 rpm, this is achieved due to high compression and optimized timing phases. Torque. It is transmitted through a single-stage gearbox, which minimizes power losses when rotating the propeller.
The most important element of the cooling system is the water pump, which drives the water from the water through the engine cooling shirt and exhaust pipes, which allows the engine to run at full speed for a long time without the risk of overheating, which distinguishes it from many competitors using simple thermosyphon cooling, but it is worth remembering that the pump depends on the cleanness of the water intake holes.
The secret of the durability of the piston group
The piston in Yamaha 3 hp has a special skirt treatment and three compression rings, which ensures excellent tightness even after prolonged use.
Below is a detailed table of the main parameters that will help you compare this model with its counterparts:
| Parameter | Meaning | Unit of measurement |
|---|---|---|
| Workload | 49.3 | cm3 |
| Maximum power | 3.0 | hp |
| Rate of rotation (WOT) | 4500-5500 | min |
| Ignition system | CDI (electronic) | - |
| Weight (no fuel) | 9.8 | kilogram |
The ignition system deserves special attention. CDI It doesn't require an external power source to operate, because the power comes from the built-in magdino, which makes it possible to start the engine in any environment, even if the boat's battery is completely drained, and electronically controlled ignition angle ensures stable operation in all modes.
Fuel consumption and preparation of the working mixture
One of the main issues that arises from owners is economy. Two-stroke engines are traditionally considered more “glutty” than four-stroke, but in the 3 hp class the difference is not so significant because of the small cylinder volume. The average consumption of AI-92 gasoline is about 0.8 – 1.0 liters per hour when driving at full gas. At trolling speeds (about 3-4 km / h), consumption is reduced to 0.4-0.5 liters.
The key to operation is the proper preparation of the fuel mixture. Since the engine does not have a separate oil crankcase, the lubrication of all rubbing parts is done with oil dissolved in gasoline. The ratio of mixing for new engines and during the break-in period is 1:25 (40 ml of oil per 1 liter of gasoline). After the first 10 hours of operation, you can switch to a standard ratio of 1:50 (20 ml of oil per 1 liter of gasoline).
⚠️ Warning: Never store the prepared fuel mixture for more than one month. Gasoline is oxidized and the oil precipitates, which can lead to candles coking and the destruction of the piston group.
It is better to use a special measuring vessel with risks for mixing, rather than acting "by eye" using a poor-quality two-stroke oil (without labeling). TC-W3Cheap oils form a lot of sodium, which clogs the exhaust windows of the cylinder, reducing power and increasing the risk of overheating.
Use only special two-stroke oils for water equipment labeled TC-W3. Automotive two-stroke oils (for motorcycles) contain additives that, when burned, form solid soak, dangerous for water cooling.
Interestingly, fuel consumption is also directly dependent on the state of the spark plug and the setting of the carburetor. If the engine "troit" or stalls when a sharp throttle opens, perhaps the mixture is too poor or rich. Adjustment is made by screws of quality and quantity on the carburetor, but it is better to entrust this procedure to professionals if you do not have experience.
Weight, dimensions and ease of transportation
When it comes to small PVC boats, every gram of weight matters. Yamaha 3bhp weighs just 9.8kg in dry condition. This makes it easy to install and remove the motor with one hand, which is especially true for single-handed fishermen or female drivers.
The handle is ergonomically positioned and allows you to carry the motor like a suitcase, and unlike some competitors, the handle does not vibrate excessively and fits comfortably in the palm of your hand. Transportation It also does not cause problems: the motor can be laid on either side, since there is no oil in the crankcase that could leak out through the glands or get into the combustion chamber.
- 🎒 Compact: perfectly fits in the trunk of a passenger sedan along with the boat.
- 🛡️ Protection: lower unit is coated with anti-corrosion coating, resistant to salt water.
- 🔄 Maneuverability: The rotary tiller allows you to control the boat in cramped conditions.
- 🔧 Maintenance: Access to the candle and draining water from the pump does not require disassembling the casing.
Despite its light weight, the design of the lower unit is massive enough to quench vibrations, which reduces hand fatigue during long-term driving, but it is worth considering that at high speeds, the motor can create a noticeable noise, characteristic of all two-strokes.
Compatibility with watercraft
The 3 horsepower is enough to plane a fully inflatable boat with one adult on board. If the load is increased to two people or heavy equipment is added, the boat will move in displacement mode at a speed of 5-7 km / h. This is ideal for quiet fishing, hunting or cruising in shallow water.
The recommended length of the boat for this engine is from 2.7 to 3.5 meters. On longer and heavier boats (more than 4 meters), the engine may not cope with the task of plane, especially in the presence of wind or wave.
The Yamaha 3 hp comes in a short-dadewood (S) version, which corresponds to a standard transom height of 381 mm (15 inches). Installing the motor on a higher or lower transom will require the use of a transition board, which can disrupt hydrodynamics and lead to cavitation.
⚠️ Warning: Don't try to reach maximum speed in shallow water. Suction of sand and silt together with water will instantly disable the impeller of the water pump, which will cause the engine to overheat in minutes.
For catamarans and flat-bottomers, this motor is also great, since they have a flat bottom and easily get on plane even with low power. The main thing is to adjust the differentiation correctly (engine angle) with the help of veneer on the lower unit.
breaking in and first service
The process of running is the foundation of a long life for you. Yamaha 2CMHSNeglecting this stage reduces the engine life by many times. The break-in should take place on a pond, not in a barrel, since the load on the engine should be real. The first tank (about 3-4 liters of the mixture) must be rolled out at revs no more than 50% of the maximum, periodically changing the gas.
☑️ Checklist of first break-in
After the first 10 hours (or two full tanks), the oil in the gearbox should be replaced, the factory may have a technical lubricant or shavings formed by grinding the gears, and it is also recommended to check the tightening of all bolt joints, as vibration may weaken them.
The spark plug after running is better twisted and inspected. The color of the coar should be brick brown. Black soda indicates a rich mixture or excess of oil, white indicates a poor mixture and overheating. Regular replacement of the candle (once a season or every 100 motor hours) guarantees a stable start.
Properly break-in on the enriched mixture (1:25) creates the necessary oil film on the cylinder mirror, preventing bullies in the future.
Frequent malfunctions and methods of their elimination
Despite the reliability, the engine can stop starting or lose power, the most common cause is contamination of the jelly carburetor or fuel filter, if the engine starts and stalls, check if gasoline enters the carburetor, often solved by blowing the fuel system.
The second most common problem is the failure of the crankshaft glands, symptoms: air suction, loss of compression, only working on the pump, replacing the glands requires disassembly of the engine and special tenants, so you better contact the service.
- 🔥 Overheating: Most often caused by a break in the impeller pump or clogging of the cooling holes.
- 💨 Power loss: Check the exhaust windows for overgrown carbon monoxide.
- ⚡ No spark: check the candle, cap and ignition coil (magdino).
Regular preservation for the winter period prolongs the life of the engine. You need to produce all the gasoline from the carburetor, oil the cylinder through the candle hole and store the engine in an upright position in a dry room.
Frequently Asked Questions (FAQ)
Can you use the Yamaha 3bhp in salt water?
Yes, the engine has a corrosion-resistant coating and stainless steel parts, which allows it to be used in seawater, but after each exit, you need to thoroughly wash the lower unit with fresh water to wash away the salt that crystallizes and breaks down the metal.
Which gasoline is better to pour: AI-92 or AI-95?
The instructions recommend using gasoline with an octane number of at least 90. In modern conditions, the best choice is a quality AI-92 with a minimum alcohol content. AI-95 often contains many additives that can more quickly disable candles and form a loam.
Why does the engine smoke when it's working?
Two-stroke engines always smoke more than four-stroke engines because of the burning of oil. However, excessive blue smoke can indicate the wrong proportion of the mixture (too much oil) or the use of low-quality oil. If the smoke is black, the mixture is too rich in gasoline.
Do I need to register a boat with this engine?
According to the current legislation of the Russian Federation (at the time of writing), the registration in the GIMS is subject to boats weighing more than 200 kg or with an engine powering more than 8 kW (about 10.8 hp). Since the Yamaha 3 hp has a power of about 2.2 kW, and PVC boats are light, registration is usually not required, but the laws may change.