Choosing an outboard motor for a small inflatable boat or a light boat is often a compromise between power and weight. When it comes to the 5 horsepower class, the size requirements become critical, as this segment is popular among solo fishermen and owners of small PVC vessels. Motor weight in this case is a determining factor affecting the transportability of the whole set and the possibility of installing it on the transom of a fragile boat.
Modern technology allows manufacturers to reduce the weight of the units without losing traction specifications. Engineers introduce light alloys, optimize the cooling system and revise the design of the daydwoot. However, not all models are the same: the difference in weight between the heaviest and lightest member of the class can reach 5-7 kilograms, which for one person carrying the motor to water is significant.
In this article, we will discuss in detail which engine can be considered the lightest in the 5 hp class, compare the technical specifications of market leaders and answer questions about the reliability of two-stroke and four-stroke circuits. You will learn whether to chase the minimum weight to the detriment of functionality and what nuances of operation are hidden behind the numbers in the specification.
Why 5 HP motor weight is crucial
For many owners of small boats boat-engine It's not just stationary equipment, it's a piece of equipment that you have to carry around, and imagine if you have to walk a few hundred meters on the shore, through sand or rocks, to get to the water, and if the motor weighs 25 kg, that's one story, and if you have 18 kg, the load on the spine and the hands is very different.
Besides, boat-sweeper PVC often has load limitations. An engine that is too heavy can disrupt the differentiation of a vessel by upside down or overly dipping the stern, affecting not only comfort but also safety: improper weighting reduces stability and handling on the wave; lightweight models allow you to maintain balance even on the most compact "cans".
⚠️ Warning: When choosing a motor, always consider the maximum recommended power and engine weight specified by the boat manufacturer in the product passport. Exceeding these parameters can lead to the destruction of the transom.
And it's also worth remembering that there are laws that can change, and in some regions, there are simplified registration or rights requirements for engines of a certain power or weight, and while 5 hp is a borderline, the weight of the unit itself affects whether you can operate it alone without the need for outside help.
Leaders of the rating: a review of the lightest models
Analyzing the market, we can identify several manufacturers that traditionally occupy the top lines in the ratings on the criterion of “weight / power”, the Japanese company has been the undisputed favorite for many years. TohatsuTheir four-stroke MFS5C weighs only 25.2 kg, a benchmark that rivals match, combining reliability and compactness.
Brand MercuryAs Tohatsu’s small power partner, it often offers similar engines under its name. For example, the Mercury F5M has almost identical weight specifications (about 25 kg), but can differ in the design of the casing and throttle settings, a great choice for those who trust the American brand but want to get Japanese build quality.
Company Suzuki It also keeps up with the DF5AS, which weighs about 25.5 kg, which is almost indistinguishable from the leaders in practice. However, Suzuki often relies on an electronic ignition system and an improved cooling system, which can be important for long-term operation at low speeds. four-strokeThis ensures low noise and efficiency.
- 🏆 Tohatsu MFS5C Weight standard of 25.2 kg, time-tested reliability and simple design.
- ⚓ Mercury F5M - analogue of Tohatsu with an updated design and excellent availability of spare parts in service centers.
- 🌊 Suzuki DF5A - slightly heavier than competitors by a couple of hundred grams, but is famous for its "unkillability" and EFI system (in some versions).
If you look at two-stroke engines, the weight category is even lighter. Tohatsu M5BDS It weighs only 19 kg. That's the absolute record if you ignore the type of engine, but two-strokes require a mixture of gasoline and oil, which is an inconvenience to many users, and they're also noisier and more voracious.
When buying a used motor, be sure to check the state of the daydvut. Light models often have magnesium alloys, which are prone to corrosion when the paint is damaged.
Two-stroke vs. four-stroke: the battle for kilograms
The eternal controversy between the two-tack (2T) and four-tack (4T) in the 5hp class is a serious one. two-stroke The difference can be from 5 to 7 kg in favor of 2T. This is achieved due to the lack of a complex lubrication system (oil crankcase), a simpler design of the head of the unit and the lack of valve mechanism.
On the other hand, four-stroke engines, although heavier, offer comfort comparable to that of a car. You don't have to think about mixing fuel, they have minimal noise and the exhaust is cleaner. For fishing, where silence is important, the 4T is the only option. In addition, the four-stroke engine is usually more resourceful thanks to a more advanced lubrication system for rubbing parts.
⚠️ Warning: Do not try to fill a four-stroke engine with a mixture of gasoline and oil, and a two-stroke engine with pure gasoline, which will cause the engine to fail instantly.
There's also a transport nuance: Four-stroke engines can't be carried on the side or upside down without the oil being drained, because it can get into the combustion chamber or the air filter. Two-strokes are more omnivorous, although they're better transported in the running position. If you plan to carry the motor in the trunk of a car often, this can be a crucial factor.
The myth of weight
Is it true that the 4T is always heavier?: Yes, the design of the 4T engine inherently more complicated. The presence of camshafts, valves, oil pump and more metal in the cylinder block inevitably adds weight.
Comparative table of specifications of top models
To make it easier for you to navigate the numbers, we've created a summary table, and here are the key parameters that influence your choices. Not only do you look at the dry weight, but you also look at the tank volume and the launch system, because they also affect the final usability.
| Model | Type of engine | Weight (kg) | Tank volume (l) | Launch |
|---|---|---|---|---|
| Tohatsu MFS5C | four-stroke | 25.2 | 0.9 (built-in) | manually |
| Mercury F5M | four-stroke | 25.0 | 0.9 (built-in) | manually |
| Suzuki DF5A | four-stroke | 25.5 | 0.9 (built-in) | manually |
| Tohatsu M5BDS | two-stroke | 19.0 | 1.1 (built-in) | manually |
| Yamaha F5CMHS | four-stroke | 27.0 | 0.9 (built-in) | manually |
As you can see from the table, lightest four-stroke engine It's a 25kg Mercury F5M, although the difference from the Tohatsu MFS5C is almost statistical. If you look at absolute weight, the two-stroke Tohatsu M5BDS wins by a huge margin. The Yamaha in this table is a slightly heavier model, which is due to the design features of the particular series.
In the 5 hp class, external tanks are rarely used, as they add the weight of the hose and the canister itself. The built-in tank, about 0.9-1.1 liters, provides approximately 4-5 hours of full gas operation or a full day of fishing in economical mode.
Technical features of light engines
To get low weight, engineers go to various tricks. One of them is using the tools. aluminum-alloy High strength for the dreadwut and bracket, but some manufacturers are experimenting with composite materials for the dreadwut, which allows for even lower weight, but increases the cost of repair in the event of an impact on an underwater obstacle.
Cooling also plays a role. Lightweight motors are most commonly used by forced water cooling with a centrifugal pump. It is important to monitor the control hole ("jet") to make sure that water circulates. Overheating is the main enemy of lightweight aluminum blocks, as they lose geometry faster at critical temperatures than cast iron shells of heavy marine engines.
- 🔧 carburetor Most lightweight motors use a simple float carburetor that requires minimal maintenance.
- 💧 Thermostat The presence of a thermostat in the cooling system helps the engine to reach operating temperature faster, reducing wear.
- ⚙️ gearbox - even in the lightest models, a full-fledged gearbox with a forward-neutral-back transfer is used, which provides excellent maneuverability.
The ignition system deserves special attention. Modern lightweight motors are equipped with electronic CDI ignition, which eliminates the need to adjust the gaps in the contacts (like in old magdinos) and provides a stable spark at all rpms. For the user, this means no problems with starting in wet weather.
☑️ Pre-purchase check
Operation and maintenance: extending the life of the motor
The maintenance of a light outboard motor does not require a complex tool, but requires regularity. winter-preservationIf you don't plan to go out for more than a month, you either need to generate fuel from the carburetor or add a stabilizer. The remaining gasoline can oxidize and clog the chicklers, leading to launch problems next season.
The second important aspect is lower unit: after each trip through salt water, the motor must be thoroughly washed with fresh water, the salt aggressively affects aluminum alloys, and it is also recommended to lubricate the mounting points and hinges of the rotary mechanism with special water-resistant lubrication to avoid sourcing.
⚠️ Warning: Never run the motor out of water without connecting to a cooling system (barrel or plumbing) and running dry for 30-60 seconds can cause the impeller pump to melt and the piston group to overheat.
Replacement of oil in a four-stroke engine is a procedure that must be performed every 50-100 hours or once a season. FC-W Automotive oils may contain additives that are harmful to the catalyst (if any) or not suitable for operation in high humidity conditions.
Regular oil change and washing of the cooling system is the guarantee that the light engine will last you 10 years or more without major repairs.
Frequently Asked Questions (FAQ)
Can I develop a planing speed on the engine 5 hp?
Yes, you can, but only on very light boats (PVC up to 3 meters long) with one person and a minimum load. The planing speed will be about 20-25 km / h. To enter plane, the correct installation of the engine in height and the angle of the transom is critical.
What kind of gasoline is best used for these engines?
For modern four-stroke 5 hp engines, it is recommended to use AI-95 gasoline. Using AI-92 is possible, but can lead to detonation at full load and reduce engine life. Always use fresh fuel.
Do I need to register a boat with a 5 hp engine?
In Russia (as of 2026) boats weighing up to 200 kg and motors up to 10.88 hp (8 kW) are not subject to registration in GIMS if their total weight does not exceed 200 kg.
Why does the engine stop at idle speed?
Most often, the cause is a polluted carburetor, air sucking through the gaskets or an incorrectly tuned idle screw, and it is also worth checking the spark plug and the fuel filter-sludge.
Choosing the lightest 5hp outboard motor is about balancing the ease of carrying with the functionality you want. Tohatsu, Mercury and Suzuki’s quarter-acting models offer the optimal combination of weight around 25kg and comfort. Two-strokes win in weight but lose in environmental and noise. With the pros and cons, you can choose the perfect unit for your conditions.