Yamaha 2.5hp Outboard Engine
Product Code: YAMF2.5 BMHL
Compact and reliable, the Yamaha 2.5hp outboard engine delivers dependable performance for small boats and dinghies. This lightweight motor features fuel-efficient operation, making it ideal for leisurely cruising and fishing trips. Built with Yamaha's trusted engineering, it offers smooth acceleration and easy handling. Perfect for boaters seeking a practical, low-maintenance solution that won't compromise on quality or durability.
- BMHS - Short shaft (15") - 17kg
-
BMHL - Long shaft (20") - 18kg
- Engine type: OHV, 1-cylinder
- Displacement: 72 cm³
- Bore x stroke: 54.0 × 31.5 mm
- Compression ratio: 8.8 : 1
- Fuel induction system: 1 carburetor
- Lubrication system: Splash lubrication
- Engine oil capacity: 0.25 L
- Ignition / advance system: CDI
- Alternator: Not available
- Overall length: 625 mm
- Overall width: 363 mm
- Overall height: S: 1028 mm, L: 1155 mm
- Engine transom height: S: 433 mm, L: 560 mm
- Steering angle: 360 degree full pivot
- Dry weight: S: 17kg, L: 18 kg
- Maximum propeller shaft output: 1.8 kW
- Full throttle operating range: 5250 – 5750 r/min
- Idling speed: 1800 – 2000 r/min
- Shallow water drive: Not available
- Gear shift: F-N
- Gear ratio: 2.08 (27/13)
- Gear oil capacity: 0.075 L
What this engine does - and what it does not
Everything below is from Yamaha's own European technical guide, linked at the foot of this page. What the engine will not do is set out just as plainly as what it will - and on this one, the right-hand list is the part to read first.
Included
- ✓The lightest engine we stock, at 17 to 18 kgOne person can carry it down a pontoon, lift it into a car boot and stow it in a cockpit locker without help. Nothing else in the range comes close.
- ✓Four-stroke, so no mixingPetrol goes in neat and the oil lives in the sump, exactly like a car engine. No two-stroke oil, no measuring, no smoke.
- ✓Short or long shaft433 mm and 560 mm transom heights, the usual 15 in and 20 in. Measure the transom before you choose - it is not adjustable afterwards.
- ✓Four trim positionsEnough to get the leg square to the water on most tenders, which is what stops the bow pushing or the prop ventilating.
- ✓About as simple as an engine getsSplash lubrication, one carburettor, TCI ignition, 0.25 L of oil. Very little to go wrong and very little to service.
- ✓Runs on ordinary unleadedYamaha specifies regular unleaded, RON 90. Nothing special from a marina pump.
Not supported
- ✗There is no reverse gearYamaha publishes the gear shift on this engine as F-N: forward and neutral. To go astern you swing the whole engine round on its mount. Every other Yamaha in this range is F-N-R. If you are coming alongside single-handed in a tide, this is the thing that will decide whether the 2.5 is the right engine for you.
- ✗It will not charge anythingThere is no alternator on this model at all - not optional, not fitted. If you want the engine to keep a battery topped up, the smallest one that can is the 8 hp.
- ✗No shallow water driveThe 4, 5 and 6 have three shallow-water positions and the bigger engines have two. This one has none, so in thin water you are trimming the leg rather than raising it.
- ✗Manual start and tiller onlyPull start and a tiller handle. There is no electric-start or remote-control version of this model, so it is a boat you steer from the back.
- ✗The smallest output in the range1.8 kW. Plenty to move a tender across a harbour, and not enough to push a loaded boat against a spring tide. If in doubt, size up.
What you get
17 kg, and that changes everything
The difference between an engine that gets used and one that stays in the garage is usually whether you can lift it on your own. This one you can.
Forward and neutral, not reverse
Worth saying twice, because it is the single most common surprise on a first small outboard. You turn the engine to back up, the way an outboard-powered tender has always been handled.
Four-stroke simplicity
Neat petrol, oil in the sump, one carburettor and splash lubrication. It starts, it runs, and there is very little of it to maintain.
Short or long shaft
433 mm or 560 mm transom height. Measure from the top of the transom straight down to the bottom of the hull and match it before you order.
Reading a Yamaha model code
Yamaha's codes are on every listing, invoice and dealer site, and nothing on the engine explains them. Take F9.9JMHS - once you can read it, the whole range makes sense in about ten seconds.
F9.9 - four-stroke, 9.9 hp
F is the four-stroke family, and the number is the horsepower at the propeller shaft. Every engine in this range is a four-stroke, so every code starts with F.
J - design revision
A letter marking which generation of that model it is. It moves on when Yamaha revises the engine, so it is how you tell a current unit from a superseded one: F9.9J is the current 9.9.
MH - manual start, tiller handle
M is manual pull start, H is a tiller handle. An E in place of the M is electric start, and a code without the H is built for remote controls rather than a tiller.
S - short shaft
S is the short shaft, L the long. On this range the two are exactly 127 mm apart - five inches - which is where the 15 in and 20 in descriptions come from.
How much engine do you actually need?
Horsepower is the number everyone looks at and rarely the one that decides it. Weight, shaft length and whether the engine has a reverse gear matter more on a small boat.
2.5 to 6 hp
A tender, a small dinghy, a yacht's shore boat. Light enough for one person to carry down a pontoon and lift onto a transom. The 4, 5 and 6 are the same 139 cc engine at three states of tune.
8 and 9.9 hp
A bigger tender, a small day boat, or a yacht that wants to push against a foul tide. Both are the same 212 cc twin - the 9.9 is the same engine tuned harder.
15 and 25 hp
Enough to get a small boat planing rather than pushing water. This is transom-bracket and two-people territory, not something you lift off at the end of the day.
Measure the transom
Short shaft suits a transom around 15 in, long shaft around 20 in. Yamaha's own figures put S and L exactly 127 mm apart on every model in this range. Too short and the propeller ventilates in a chop; too long and you drag the leg.
F2.5
Every figure below comes from Yamaha's own European technical guide for the F2.5B.
| Yamaha model code | F2.5BMH |
|---|---|
| Engine type | OHV, 1 cylinder |
| Displacement | 72 cm3 |
| Bore x stroke | 54.0 x 31.5 mm |
| Compression ratio | 8.8 :1 |
| Fuel induction | 1 carburettor |
| Maximum output at the propeller shaft | 1.8 kW (2.5 ps) |
| Full throttle operating range | 5250 to 5750 r/min |
| Lubrication | Splash lubrication |
| Ignition | TCI |
| Alternator | Not fitted |
| Gear shift | F-N. No reverse gear |
| Gear ratio | 2.08 (27/13) |
| Trim | 4 positions |
| Transom height | S 433 mm, L 560 mm |
| Dry weight | 17, 18 kg |
| Engine oil capacity | 0.25 L |
| Gear oil capacity | 0.075 L |
| Recommended fuel | Unleaded regular, RON 90 |
Fitting it
- Match the shaft length to the transom before anything else - S for around 15 in, L for around 20 in.
- Check the boat's maximum power plate. That figure is the ceiling, whatever the transom will physically carry.
- Unleaded regular, RON 90. Fuel goes in neat - the oil lives in the sump.
- Rinse through with fresh water after salt, and stow the engine upright so the leg drains.
- On a small tender, fit a safety lanyard and use it. It is the one piece of kit that only matters once.
Every Yamaha outboard we stock
Live prices and the figures Yamaha publishes in their own European technical guide. Every column links to that guide.
| Model | F2.5 2.5 hp | F4 4 hp | F5 5 hp | F6 6 hp | F8 8 hp | F9.9 9.9 hp | F15 15 hp | F25 25 hp |
|---|---|---|---|---|---|---|---|---|
| You are viewing | ||||||||
| Model code | F2.5BMH | F4BMH | F5AMH | F6CMH | F8FMH | F9.9JMH | F15CMH | F25GMH |
| Engine | OHV, 1 cylinder | OHV, 1 cylinder | OHV, 1 cylinder | OHV, 1 cylinder | SOHC, in-line 2 | SOHC, in-line 2 | SOHC, in-line 2 | SOHC, in-line 2 |
| Displacement | 72 cm3 | 139 cm3 | 139 cm3 | 139 cm3 | 212 cm3 | 212 cm3 | 362 cm3 | 432 cm3 |
| Max output | 1.8 kW (2.5 ps) | 2.9 kW (4 ps) | 3.7 kW (5 ps) | 4.4 kW (6 ps) | 5.9 kW (8 ps) | 7.3 kW (9.9 ps) | 11.0 kW (15 ps) | 18.4 kW (25 ps) |
| Full throttle range | 5250-5750 r/min | 4000-5000 r/min | 4500-5500 r/min | 4500-5500 r/min | 5000-6000 r/min | 5000-6000 r/min | 5000-6000 r/min | 5000-6000 r/min |
| Compression | 8.8 :1 | 8.9 :1 | 8.9 :1 | 8.9 :1 | 9.4 :1 | 9.4 :1 | 9.3 :1 | 9.1 :1 |
| Ignition | TCI | CDI | CDI | CDI | CDI | CDI | CDI | TCI |
| Alternator | None | 6 A optional | 6 A optional | 6 A optional | 6 A | None on MH | None on MH | 16 A |
| Gear shift | F-N only | F-N-R | F-N-R | F-N-R | F-N-R | F-N-R | F-N-R | F-N-R |
| Gear ratio | 2.08 (27/13) | 2.08 (27/13) | 2.08 (27/13) | 2.08 (27/13) | 2.08 (27/13) | 2.08 (27/13) | 2.08 (27/13) | 2.08 (27/13) |
| Shallow water drive | None | 3 positions | 3 positions | 3 positions | Manual, 2 positions | Manual, 2 positions | Manual, 2 positions | Manual, 2 positions |
| Trim | 4 positions | 5 positions | 5 positions | 5 positions | 4 positions | 4 positions | 4 positions | Manual, 4 positions |
| Transom height | S 433 mm / L 560 mm | S 435 mm / L 562 mm | S 435 mm / L 562 mm | S 435 mm / L 562 mm | S 431 mm / L 558 mm | S 431 mm / L 558 mm | S 438 mm / L 565 mm | S 424 mm / L 551 mm |
| Dry weight | 17, 18 kg | 27, 28 kg | 27, 28 kg | 27, 28 kg | 40-43 kg | 40-45 kg | 51-61 kg | 56-70 kg |
| Engine oil | 0.25 L | 0.6 L | 0.6 L | 0.6 L | 0.8 L | 0.8 L | 1.8 L with filter change | 1.1 L with filter change |
| Gear oil | 0.075 L | 0.100 L | 0.100 L | 0.100 L | 0.150 L | 0.150 L | 0.250 L | 0.370 L |
| Price | £670 £805 | £1,035 £1,220 | £1,110 £1,310 | £1,232 £1,460 | £1,925 £2,270 | £2,175 £2,825 | £2,320 £2,730 | £3,561 £4,190 |
| Yamaha specification | ||||||||
| View product | You are here | F4 | F5 | F6 | F8 | F9.9 | F15 | F25 |
Choosing an outboard
Three questions settle it, and only one of them is about horsepower.
What is the boat rated for?
Most boats carry a plate stating a maximum engine power and often a maximum weight on the transom. That is the ceiling. Fitting more than the plate allows affects handling and, on an inflatable, can lift the bow in a way that is genuinely dangerous.
If there is no plate, tell us the make, length and construction and we will work it out with you.
Short shaft or long?
Measure from the top of the transom straight down to the bottom of the hull. Around 15 in wants a short shaft, around 20 in a long one. Get it wrong and the engine either ventilates when the boat pitches or drags its leg through the water all day.
This is the single most common ordering mistake, and it is not something you can adjust out afterwards.
How often will you lift it?
An engine that lives on the transom can be as heavy as the boat allows. One that gets carried down a pontoon, lifted into a car boot or stowed in a locker has a practical limit well below the legal one - 17 kg is a different proposition from 45 kg every weekend.
Be honest about this. It is the reason people end up not using a perfectly good engine.
What you will also want
You may also need
Yamaha outboard FAQs
Does it have reverse?
Will it charge a battery?
Is 2.5 hp enough for my tender?
Which shaft length do I need?
Will it fit my boat?
What fuel does it take?
It is a four-stroke - do I mix oil with the fuel?
Can I use it in salt water?
How long will it take to arrive?
Not sure which one?
Tell us the boat, the transom height and how often you will be lifting the engine, and we will tell you which Yamaha to buy - including when the smaller one is the right answer.
Talk to the chandlery
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