Choosing an outboard motor for a medium-sized boat is always about balancing power, weight and efficiency. Yamaha outboard motor 70 four-stroke It has established itself as one of the market leaders, offering the perfect combination of performance and reliability. Owners of 4 to 6-meter long PVC boats and boats often pay attention to this model, as it is able to provide a confident plane even at full load.
The four-stroke design is very different from the two-stroke design, offering reduced noise and vibration, making it much more comfortable to be on the water, allowing you to enjoy the silence of nature or quiet conversation. Yamaha introduced advanced combustion technologies into this series, which has a positive effect on the environment and the owner’s wallet.
In this article, we will discuss in detail the technical nuances, features of operation and advantages of this power plant. You will learn why many anglers and boaters prefer this unit for their tasks. Understanding the specifics of the engine will help you make an informed decision about the purchase or modernization of current equipment.
Technical specifications and design features
At the heart of the unit is a reliable 4-cylinder internal combustion engine with a volume of 1152 cubic centimeters, which ensures smooth operation at all speeds and excellent traction at low speeds, which is critical for trolling fishing. SOHC (camshaft in the head of the block) simplifies the design of the gas distribution mechanism, increasing its durability.
The control system is important. The motor is equipped with an electronic throttle. Y-CET Yamaha Computer Controlled Electronic Throttle, which provides precise throttle control, not only improves the engine's response to the gas handle, but also allows you to implement the trolling function without having to keep your hand on the tiller. The dry weight of the structure is about 115-118 kg, which is the average for this power class.
⚠️ Attention: When installing the motor on a transom, make sure that the transomboard can withstand the weight of more than 115 kg in static and dynamic loads when driving.
The cooling system is based on the principle of taking water from a reservoir through water intakes in lower unit, which allows the engine to quickly reach the operating temperature and maintain it even in cold water, which reduces the wear of rubbing parts and optimizes the combustion of the fuel mixture.
LITEST Technology
The LITEST (Lean Burn Control System) system automatically adjusts the ignition angle and composition of the mixture depending on the load, ensuring maximum combustion efficiency and reducing fuel consumption at cruising speeds.
Economy and fuel consumption
One of the main arguments in favor of four-stroke engines is their fuel efficiency. Yamaha 70 It consumes significantly less gasoline than two-stroke analogues of the same power, and when idling, the consumption is minimal, allowing you to drift for a long time or expect a stick without fear of emptying the tank.
Real fuel consumption depends on a variety of factors: boat weight, propeller condition, weather conditions and driving style. On average, when driving in economical mode (about 3,500-4000 rpm), the engine consumes about 15-18 liters per hour. At maximum speeds, this figure can reach 25-28 liters, but in this mode the engine works for a short time.
- 🔹 Fuel savings of up to 50% compared to two-stroke engines of similar power.
- 🔹 The ability to use tanks with a capacity of 25 liters (standard) or connect to external tanks through the system
Multi-Function Tiller. - 🔹 No need to mix oil with gasoline, which makes it easier to refuel.
- 🔹 Stable consumption on long transitions thanks to the electronic fuel injection system.
You can use a formula that takes into account the tank volume and the average flow rate, for example, with a tank of 100 liters and an average flow rate of 20 liters per hour, you can walk about 250-300 kilometers at cruising speed, which makes the engine an excellent choice for long-distance expeditions.
Comparison with two-stroke analogues
When choosing between two-stroke and four-stroke engines, there is often a dilemma. Two-strokes are traditionally lighter and cheaper, but they are not. Yamaha outboard motor 70 four-stroke It overcomes these disadvantages with its advantages, primarily resource and environmental friendliness.
Two-stroke engines burn a mixture of oil and gasoline, throwing some of the unburned fuel into the water. Four-stroke units have a separate lubrication system, which eliminates the release of oil into the reservoir. This is especially important for anglers who care about nature and want to fish in clean water without the smell of exhaust fumes.
Noise is another critical parameter. A four-stroke cycle provides a quieter run. Yamaha F70 It's hard to see, whereas a two-stroke motor makes a characteristic high ringing, and for those who like silence on the water, the choice is obvious.
| Parameter | Yamaha F70 (four-stroke) | Analogue (two-stroke) | Advantage |
|---|---|---|---|
| Fuel consumption | ~18 l/h (medium) | ~28 l/h (medium) | Savings ~35% |
| Noise level | Low (78-82 dB) | High (90+dB) | Comfort. |
| Engine resource | High (3000+ motor hours) | Medium (1500-2000 motor hours) | Durability |
| Weight. | 115-118 kg | 95-105 kg | two-stroke lighter |
Despite the greater weight, a four-stroke motor often balances the boat better, shifting the center of gravity, but when mounted on lightweight inflatable boats, the difference in weight can be noticeable during transportation.
Maintenance and maintenance
Regular maintenance is the key to the long life of your engine. Yamaha outboard motor 70 four-stroke The first oil change must be made after the first 20 hours of running in order to remove metal shavings formed during grinding parts.
Then, the maintenance is carried out every 100 hours or once a year, the list of mandatory procedures includes the replacement of engine oil, oil filter, checking spark plugs and lubricating syringes. Yamaha Ensure that all systems work properly.
☑️ Checklist TO (100 motor hours)
⚠️ Warning: Do not use motor oils for outboard motors. They do not have the necessary anti-corrosion properties and can lead to emulsification (water entering the oil) and rapid engine failure.
It is also important to monitor the cooling system. Check the water's control stream regularly. If it becomes weaker or disappears, immediately turn off the engine, which may indicate that the water intakes are clogged with grass or sand, or that the water pump is malfunctioning.
For storage in the off-season, it is recommended to treat the engine with a preservative. You can use a spray to preserve the cylinders or simply let the engine produce the residue of fuel from the carburetor (if any) or fuel ramp.
Installation and setup on the boat
The correct installation of the motor on the transom affects the driving performance and fuel consumption. The height of the installation should be such that the anti-cavitation stove is on the same level with the bottom of the boat or 2-3 cm higher. Too low landing will increase the water resistance, and too high will lead to air capture and overheating.
The dividing angle of the lower unit also requires adjustment. For most boats, the optimal position is to have the bow slightly raised in the planing, adjust it with a tilt pin on the transom plate, experiment with the holes to find a position with minimal resistance.
Before your first trip, be sure to check the tightening of all the motor-trans anchor bolts and the lower unit fastening nuts. Vibration at the first starts can weaken the connections.
The standard propeller allows the motor to reach maximum speeds (5500-6000 rpm) at an average boat load. If the engine does not spin and does not reach maximum speed, the screw pitch is large. If the engine "twistles" (rpm above 6200), the screw pitch should be increased.
For heavy boats or frequent cargo transportation, it makes sense to buy a second, more "traction" propeller with a smaller pitch, which will allow you to confidently go to the plane and save engine life without working at the limit of possibilities.
Typical malfunctions and methods of their elimination
Despite the high reliability, the equipment can fail. Most often problems are related to the quality of the fuel or the ignition system. If the engine starts poorly or stalls, first check the candles. Black coating will indicate a rich mixture, white - poor or overheating.
Fluid fuel filters are a common cause of power loss, and the tank may contain water or dirt, and an additional fuel filter sediment between the tank and the engine is recommended to protect the expensive fuel system. Yamaha.
- 🔹 The engine does not start: check for spark and fuel supply.
- 🔹 The engine is unstable: clean or replace the candles, check the fuel hoses for cracks.
- 🔹 Overheating: Check the control trickle, clean the water intakes, check the thermostat.
- 🔹 Vibration: Check the screw balancing and no blade damage.
If you hear a foreign knock or a grinding in lower unit, stop operating immediately, which may indicate damage to gear gear gears or hitting a foreign object, and further work will lead to expensive repairs.
Timely diagnosis and use of high-quality fuel with an octane number of at least AI-95 prevent 90% of possible engine failures.
Conclusion and recommendations on selection
Yamaha outboard motor 70 four-stroke It's an investment in comfort and reliability, ideal for owners of 4.5-6-meter boats who value efficiency and quiet running, and despite the higher initial cost compared to two-stroke boats, it quickly pays off with fuel savings and no need for constant oil additions.
When buying, pay attention to the availability of official warranty and service support in your area. Original parts and skilled mechanics are an important part of owning such equipment.
By choosing this motor, you get a time-tested technology that will allow you to spend more time on the water doing what you love, not repairing. 70 hp is enough for outdoor activities, water skiing and serious fishing.
What is the best gas to fill in Yamaha 70?
It is recommended to use unleaded gasoline with an octane number of 95 (AI-95) or higher. Using fuel with a low octane number can cause detonation and damage the piston group.
Do I need to dilute the oil with gasoline?
No, Yamaha F70 It's a four-stroke engine with a separate lubrication system, and the oil is put in the crankcase, and the tank is filled with pure gasoline.
How often should you change the oil in the gearbox?
The oil in the gearbox is recommended to be changed once a year or every 100 motor hours. At the first maintenance after running (20 hours), it is not necessary to replace it, but it is desirable to check its condition.
Can this motor be used in salt water?
Yes, the engine is corrosion-resistant, but after each release into salt water, the cooling system and the outer surfaces must be thoroughly washed with fresh water to avoid corrosion.