Yamaha 25hp Outboard Motor
Product Code: YAMF25GMHS�
The Yamaha 25hp Outboard Motor delivers reliable performance for small to medium-sized boats. This compact yet powerful engine combines fuel efficiency with smooth operation, making it ideal for recreational fishing, cruising, and water sports. Built with Yamaha's trusted engineering, it features dependable starting, low vibration, and minimal maintenance requirements. Perfect for boaters seeking a balance of power and practicality without the bulk of larger motors.
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Engine type |
SOHC, In-line 2 cylinders |
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Displacement |
432 cm³ |
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Bore x stroke |
65.0 × 65.1 mm |
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Compression ratio |
9.1 : 1 |
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Fuel induction system |
Fuel injection |
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Lubrication system |
Wet sump |
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Engine oil capacity |
1.1 L / 1.0 L (with / without oil filter replacement) |
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Ignition / advance system |
TCI |
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Alternator |
16 A |
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Overall length |
MH, WH, WHP: 1130 mm, WHT, WHD: 1129 mm |
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Overall width |
378 mm |
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Overall height |
S: 1106 mm, L: 1233 mm, X: 1320 mm |
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Engine transom height |
S: 424 mm, S (ET, WT, WHT): 429 mm, L: 551 mm, L (ET, WT, WHT, WHD): 553 mm, X: 640 mm |
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Steering angle |
45 degrees each direction |
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Dry weight |
56 kg - 70 kg |
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Maximum propeller shaft output |
18.4 kW |
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Full throttle operating range |
5000 – 6000 r/min |
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Idling speed |
850 – 950 r/min |
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Shallow water drive |
Manual: 2 positions, ET, WT: PTT: variable position |
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Gear shift |
F-N-R |
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Gear ratio |
2.08 (27/13) |
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Gear oil capacity |
0.370 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.
Included
- ✓The only fuel-injected engine in this rangeEvery other Yamaha here runs a carburettor. Injection means no choke, easier cold starting, and far less trouble from fuel left standing over a winter - which is the commonest reason a small outboard will not start in spring.
- ✓16 A of charging, as standardThe most in the range by a distance. The 8 hp manages 6 A and the tiller 9.9 and 15 have none at all, so if the boat has electronics to keep alive this is the engine that does it properly.
- ✓432 cm3 and 18.4 kWA near-square 65.0 x 65.1 mm bore and stroke. Enough to plane a small boat properly rather than push it along.
- ✓Idles lower than anything else here850 to 950 r/min against 1000 to 1100 for the twins below it. Noticeable when you are manoeuvring in a marina or trolling.
- ✓A proper reverse gear and shallow water driveF-N-R, two shallow-water positions and four trim positions.
- ✓A serviceable oil filter1.1 L with a filter change, 1.0 L without.
Not supported
- ✗The heaviest engine we stock56 to 70 kg depending on specification. This is a permanent transom fitting and a two-person job to move. Check the boat is plated for the weight as well as the power.
- ✗Check the boat's rating carefully25 hp is well beyond what most tenders and small inflatables are plated for. That plate is the ceiling regardless of what the transom will physically carry, and exceeding it affects handling.
- ✗Manual start on a 432 cm3 twinThe version we stock is MH - manual start with a tiller handle. Injection makes it start far more willingly than a carburetted engine of this size, but it is still a pull start on the largest engine here.
- ✗Tiller steering, not remoteYou steer from the back. The remote-control versions are different model codes we do not stock.
What you get
Fuel injection
The only engine in this range with it. No choke, better cold starting, and much less bother after a winter standing still.
16 A alternator
Standard, and the most in the range. The 8 hp gives 6 A and the tiller 9.9 and 15 give none.
432 cm3, near-square
65.0 x 65.1 mm bore and stroke for 18.4 kW. Enough to get a small boat properly on the plane.
A permanent fitting
56 to 70 kg. Bolt it on, wire it up and leave it - and check the transom is plated for the weight as well as the power.
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.
F25
Every figure below comes from Yamaha's own European technical guide for the F25G.
| Yamaha model code | F25GMH |
|---|---|
| Engine type | SOHC, in-line 2 cylinder |
| Displacement | 432 cm3 |
| Bore x stroke | 65.0 x 65.1 mm |
| Compression ratio | 9.1 :1 |
| Fuel induction | Fuel injection |
| Maximum output at the propeller shaft | 18.4 kW (25 ps) |
| Full throttle operating range | 5000 to 6000 r/min |
| Idling speed | 850 to 950 r/min |
| Lubrication | Wet sump |
| Ignition | TCI |
| Alternator | 16 A |
| Starting | Manual |
| Control | Tiller handle |
| Gear shift | F-N-R |
| Gear ratio | 2.08 (27/13) |
| Shallow water drive | Manual, 2 positions |
| Trim | Manual, 4 positions |
| Transom height | S 424 mm, L 551 mm |
| Dry weight | 56 to 70 kg |
| Engine oil capacity | 1.1 L with filter change, 1.0 L without |
| Gear oil capacity | 0.370 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 | £558.33 £670.83 | £862.50 £1,016.67 | £925 £1,091.67 | £1,026.67 £1,216.67 | £1,604.17 £1,891.67 | £1,812.50 £2,354.17 | £1,933.33 £2,275 | £2,967.50 £3,491.67 |
| Yamaha specification | ||||||||
| View product | F2.5 | F4 | F5 | F6 | F8 | F9.9 | F15 | You are here |
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
What does fuel injection actually get me?
Will it charge a battery?
Is 25 hp too much for my boat?
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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