• For so compact and unassuming an engine to provide so appealing a drive comes as a very pleasant surprise indeed.
  •  … the size, weight and fuss-free usability of these potent little motors put them right at the forefront of their field.
  • … the pickup is surprisingly agile, the user interface is superb, the economy is family-friendly and the tiller ergonomics are nigh-on perfect.

Yamaha F25G and F100F
Alex Smith heads for Helsinki to examine a pair of new outboard engines from Yamaha.
Let’s face it, most modern 4-stroke engines from the established marine manufacturers are compact, quiet, powerful, refined and generally very pleasing pieces of equipment. They also tend to be quite complex and expensive, but we can forgive them such sins because of the serene, frugal, fuss-free reliability they so commonly provide. Whether we use our boats daily or (more likely) abuse them sporadically, they tend to take what they’re given and behave with impeccable manners.
The majority of tests on 4-stroke outboard engines have therefore become exercises in applied pedantry. We split hairs to divide one engine from another when, in isolation, each and every one of them would keep us largely content. However, in several crucial regards, these two new motors from Yamaha buck that trend with distinctions that set them squarely apart from the current crop …

The F25G
Yamaha’s new F25G is a 432cc, two-cylinder, four-valve engine with a single overhead camshaft. As a relatively small block in a market dominated by three-cylinder units, you would expect the new Yam to be relatively light, but at 56kg it’s not just 25% lighter than its predecessor, it’s almost on a par with Yamaha’s own 362cc F20. At nearly £3,500, it does cost £610 (20%) more than the F20, but given that the 747cc F30 weighs closer to 100kg and costs £5,149, it’s actually very easy to see the sense behind the new motor for those with weight-sensitive transoms and cost-sensitive wallets.
However, while minimal weight and compact proportions were a vital part of the new design, convenience was also a priority. To that end, portability and storage have been made even easier courtesy of a new carry handle and a pair of resting pads – and to help with routine maintenance, Yamaha have also included an easy-access hose connector on the lower cowling, enabling you to flush salt away without having to start the engine.
When you try this engine on the water, the sheer ease of the user experience becomes even more pronounced. For instance, even on a compact boat like the Linder Sportsman 445, the transom feels distinctly uncluttered – and although there is some notable vibration with the leg trimmed hard in against the stop and the revs at idle, when you give it a notch of trim and increase the revs beyond 1050rpm, the experience becomes supremely smooth.
The tiller handle is also an outstanding example of its type, with an oversized gear selection switch that is positioned not on an impractical part of the cowling, but directly on the lever, within easy reach of your throttle hand. The angle of steerage is also very generous when close-quarter manoeuvres are required, and the travel of the twist grip is relatively short, which makes an extended trip at varying speeds much more comfortable on your wrist.
Now I appreciate that this all sounds like relatively minor stuff, but the collective impact is compelling. Even on a boat you’ve never helmed, the moment you fire up the engine and take the tiller in hand, the slick ergonomic simplicity of the F25 makes everything natural, intuitive and confidence-inspiring.
However, it has to be said that the ease and consistency of the starting pull is not what we had hoped. We’d been promised ‘the industry’s only one-pull start’, but when I started the engine, as well as on the nine or ten occasions I witnessed it in the hands of somebody else, it took at least two pulls to kick it into life. Happily, however, the trolling system (VTS) is bang on the money. With either tiller or remote applications, it’s very easy to operate, and rather than sitting at a standard idle of around 900rpm, it enables you to set the revs at 50rpm increments from 750 to 1050 and to tailor your speed precisely as your fishing trip demands.
As long as your weight distribution is relatively even, the pickup is also very good – and not just on skittish flat-bottomed tinnies, but on boats that hover around the 300kg mark. Even without a tiller extension, it’s not an endless battle merely to mount your own hump. On the contrary, on all three of our test boats (the Buster S, Linder 445 and Pioner 14), shifting the co-pilot forward saw us planing within 8 seconds. With its flex-happy polyethylene construction, remote console and two men on board, the Pioner 14 was a particular challenge, and yet the F25 again came through with flying colours – not just propelling the boat to a top end approaching 25 knots, but moving it in a way that brought authentic driving pleasure to the man at the helm. For so compact and unassuming an engine to provide so appealing a drive comes as a very pleasant surprise indeed.


  • Excellent tiller handle
  • Remarkably light weight
  • Impressively compact size
  • Easy trolling system
  • Refined on the plane


  • Premium price
  • Vibration at idle
  • The ‘one-pull start’ is a misnomer

F25G Specifications
Engine type: 2-cylinder, 4-valve, SOHC 4-stroke
Displacement: 432cc
Weight: From 56kg

From £3,469

The F100F
The new F100F, the fifth version of Yamaha’s 100hp 4-stroke outboard, uses a new 1.8L inline four-cylinder block with 16 valves and a single overhead camshaft. It’s all contained within a new lightweight cowling with side air intakes and an inner shell for improved water separation – and in addition to a new lower unit, the F100 also comes with a new series of propellers.
Like the F25G, weight is a major plus, with a figure of 162kg making it 7kg lighter than its predecessor and 20kg (or around 9%) lighter than the Suzuki DF100. The single-cylinder power trim and tilt function further reduces weight and bulk, and while that helps put it at the top of its class, really the chief design priorities for the new F100 were acceleration and economy – and in both regards it does very well.
On the Yamarin Cross 60C, a substantial 20ft cabin boat that weighs a metric tonne and has a power rating of up to 150hp, we achieved 31 knots at 5650rpm and a cruising speed of 22 knots with a fuel flow in the region of 0.8 litres per nautical mile. On the lighter test boats, a Finnmaster 55SC, a Buster XL and a Grand RIB G580, the engine was able to spin more freely, nudging up to 5850rpm and bringing relatively easy 35-knot performance from all three platforms.
However, the RIB was a particular surprise. Despite enjoying a maximum power rating of 150hp and incurring the drag of the collar’s aft end, which seemed perpetually dipped in the water, we were planing in just 3 seconds and hitting 30 knots in just 10. Even the 35-knot top end was achievable from a standstill in less than 15 seconds, and the economy was equally pleasing, with a gentle 20-knot cruise bringing a fuel flow of less than 0.6 litres per nautical mile. In fairness to Yamaha, they could easily have cherry-picked some nimble, light-footed boats that were much easier to lift, push and steer than this, but despite the challenges posed in terms of hole shot and throttle response, the F100 did a truly outstanding job on each and every platform.
As regards refinement, well, that’s a difficult one to assess. The F100 is by no means the quietest engine you can buy. In fact, on the Yamarin, where the cabin trapped and amplified the noise, the F100 seemed relatively unrefined by modern standards. According to Yamaha, the use of a new intake manifold and silencer ought to make it quieter and more refined than its predecessor, but even if we agree to disagree, any perceived failings of refinement in this regard are counterbalanced by conspicuous triumphs of refinement in another. In particular, Yamaha’s ‘Shock Damping System’ (SDS), which uses rubber inserts in the prop bushing, is extremely effective, bringing very smooth but positive engagement of drive and allowing you to get on with the job of enjoying an engine that performs with impressive authority.


  • Rapid hole shot
  • Engaging throttle response
  • Impressive running economy
  • Class-leading weight
  • Ideal for water sports


  • Premium price
  • Not as quiet as some

F100F Specifications
Engine type: 4-cylinder, 16-valve, SOHC 4-stroke
Displacement: 1832cc
Weight: 162kg

From £10,299

There’s really not much here to dislike. At seven or eight per cent more than the industry standard, these premium outboards do of course come with premium prices, but they back that up with features that give the boater moments of tangible, smile-inducing satisfaction. Despite their diminutive dimensions and class-leading weights, the pickup is surprisingly agile, the user interface is superb, the economy is family-friendly and the tiller ergonomics are nigh on perfect. Of course, in terms of performance, despite some impressive pickup from both models, it’s a stretch to suggest that these engines will satisfy those who continue to lament the demise of the traditional 2-stroke. But even by the standards of the modern 4-stroke outboard, the size, weight and fuss-free usability of these potent little motors put them right at the forefront of their field.

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