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The significantly light weight of the New Yamaha F70 4-stroke outboard is remarkable, and yet at the same time it delivers some real grunt.

Yamaha’s newly released 70hp 4-stroke is probably the most significant new outboard so far this century. Are these strong words true or just marketing hype? Well maybe it’s a little bit of the latter; but then, what’s remarkable about the recently-released Yamaha F70 (F for four stroke, 70 for 70hp) is that there’s not so much of the hard sell as there is of the strong words and true.

Since the good old days of 3-cylinder 70hp 2-strokes, there’s been a burning need for 70hp 4-strokes to lose some weight. Let me explain at this point that the F70 at 120kg weighs just 15 kg more than Yamaha’s own (now) classic 2-stroke 3-cylinder 70, which pulled the scales down to 105kg. That the new F70 only weighs 15kg more means the weight gap between 2-strokes and 4-strokes has at long last become manageable!

First-generation carburetored 70hp 4-strokes were up to 60kg heavier than the established 2-strokes and many boats, even hulls rated to 70hp and more, simply couldn’t handle the extra weight. In the meantime of course, while 4-strokes were first becoming popular, quite a few hulls were redesigned and modified to support the newcomers. And I guess it’s fair to observe that this worked very well in some cases — and not very well at all in others.

It’s fair to say too that those first 70hp 4-strokes lacked the familiar power delivery of the tried-and-true 3 cylinder 2-strokes. If you wanted to follow your conscience and go with a 4-stroke, you faced a choice between accepting less available power as the price you had to pay, or a good ol’ (noticeably punchier yet less environmentally friendly, and definitely much noisier) 3-pot 2-stroke screamer. And that’s not to mention the significantly higher cost of the 4-stroke option. This in itself was enough to tip the balance for many of us who elected to stay with a traditional 2-stroke and spend what was left in the pot on an electric.

Whichever way you jumped, it was never an easy choice. I’ve heard it said that the extra cost and added weight of early 70hp 4-strokes maintained 2-stroke sales for some years.

Then came a second generation of 70hp 4-strokes, bringing electronic fuel injection and computer-managed ignition systems into the equation. Any perceivable lack of power was history.

However, Yamaha’s range jumped straight from 60hp to 80hp.

So, with lack of power at the prop no longer an issue, it was back to the one concern that never went away — sheer weight.

Enter the F70. At 120kg it compares with Suzuki’s 70 at 155kg. And Honda’s latest 70 at 163kg. Then there’s Mercury’s traditional 2-stroke 75 at 138 kg; and their 75 hp 4-stroke at 180 kg. Even BRP’s 75 high tech “E Tec” 2-stroke weighs in at 145 kg.

To put this in perspective, you know you really can’t fault any of these motors; we’re well and truly spoilt for choice here. Bloody good is how outboards have to be in 2010 or they don’t survive in the marketplace.

There’s no avoiding either that weight comparisons with traditional 2-strokes are basically unfair in that a 4-stroke has heaps more moving parts. New tech 2-strokes suffer from the same thing, albeit not perhaps to quite the same degree, and that’s obviously reflected in what a set of scales has to say.

So how can the F70 be so much lighter then? It seems a good question doesn’t it.

In large part the answer lies in that the F70 is a one litre engine; 996cc to be exact. Suzuki’s 70 is 1502cc. Mercury’s 75 is 1732cc, Honda’s 70 is 1496.

Unlike competitors whose 70s are detuned versions of their 80hp and 90hp models, the Yamaha F70 has the same piston displacement as its 60.

Being a rev head of some vintage, this immediately raised a couple of flags in my mind. Along with memories of highly-tuned 1 litre motors in the past came suspicions the F70 may be a peaky beast lacking low-end and mid-rev-range grunt and needing a heap of rpms to perform. Longevity is another issue that crops up immediately. Getting power out of small engines has never been the problem but making them last a decent length of time has.

At the F70’s launch came an opportunity to get some answers on these questions so being a person never shy to ask straight questions I put the matter of longevity to Yamaha’s technical people. As you’d expect, their answers contained lots of words, which I’ll boil down to technology developed by Yamaha in other applications.

They pointed out how long Yamaha’s (much more highly tuned and much higher revving) motorcycle engines last. And speaking of motorcycles, fellow rev heads will be well aware that much of Yamaha’s Moto GP success has to do with a certain Valentino Rossi; a man who most would agree is the greatest motorcycle racer of all time.

However, as the pundits say, to finish first, first you have to finish. And with individual Moto GP engines now being regulated for use — and having to be competitive — for several races, let’s just say that Rossi’s genius can’t be fulfilled if his bike craps itself.

I suppose the tech’s smug confidence in the F70’s longevity could be said to have a solid base…

As for the peaky high-revving nature I suspected may come with a tuned-up 1 litre motor, my questions there disappeared when I got out on the water in two boats running fresh out of the box F70s. Yamaha had a new Cruise Craft Explorer 485 and a Sea Jay 4.85 Haven (plate aluminium) side console on the Brisbane River for the boating press to try.

Amongst today’s 4-stroke outboards, the 6300 rpm both boats peaked at is unremarkable. At that, the Sea Jay ran up to 60.9 km/h and the Cruise Craft 54.4. But it was how effortlessly they attained planing speeds and the grunt available at cruising speeds which left a lasting impression on me. Amongst my boating writer colleagues, I’m the lightweight of the pack, and both boats were loaded with 3 and 4 of us at a time. Neither hull is exactly a lightweight to start with so this was an impressive display of power delivery across the entire rev range. The exact opposite of any suspicion the F70 might prove “peaky.”

Since then, I’ve fully tested both boats (look for the Sea Jay in a forthcoming BBB) and I’m happy to relate nothing less than a highly-favourable impression of the F70.

Allowing for how good its competitors are and that the F70 meets them toe to toe in every respect, its significant weight reduction is remarkable. The only question left is whether it represents a third generation of lightweight and powerful 4-stroke outboards? I think the answer to that has to be yes. At the very least Yamaha’s new F70 leaves some admirable competitors playing catch up.


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