Yamaha's torquey new 70
Four-stroke outboards, and especially those in the lower horsepower range, are being born with more grunt.Words – Rick Huckstepp
-- ambient noise levels very acceptable at all RPM
Only yesterday my computer technician got called out onto Moreton Bay to tow a mate home. Said mate was running a 50hp two-stroke and the call came in via mobile: “I think I’ve blown my power head; it’s making a ticking noise and has lost its grunt.” Sounds familiar? I know the feeling; about $3000 worth in fact.
Removing a spark plug indicated bits of metal on the electrode; yep, off to the doctor; it was going to hurt!
Do you fix it or do you move onwards and upwards and join the growing throng of happy four-stroke owners; your call but eventually, someone or something else will make that call for you if you don’t.
You just need to hope you are within help’s range when it happens and not riding a wave during a dangerous bar crossing on the way home from outside.
When it comes to mid-range outboards (under 80hp) trends indicate boaters have flocked to the 4.5m to 5.0m range of boats with smaller horsepowers (under 80). In those states alone, 165,000 boat owners in that league back up the figures.
With these figures bandied around, little wonder Yamaha were keen to announce the arrival of their F70A four-stroke engine which slides nicely onto that class of boat transom.
While their 60hp F60A remains a big player in the market, this latest engine could be seen to be aimed squarely at the repower market and to those looking to max out their power options on smaller, more economical boats. (My computer mechanic’s mate who blew his 50 two-stroke has an option to power up to 70hp. My latest communication indicates that is the direction he is going and me thinks he won’t be alone).
Interestingly, figures to date indicate Yamaha’s F60A sales have not been affected by the release of the F70A. Now you could extrapolate some prognosis from this such as:
1. Is there an influx of first-time recreational boaters into the market?
2. Are current boaters re-branding their transoms?
3. Are people down-sizing from bigger boats or adding to their flotilla?
Well only time will tell on either question.
The push with this new engine by the Yamaha engineers has been one of ‘upmanship’ in the power-to-weight ratio with competitor brands.
Nothing new there; it is a competitive market and one where there is no possibility in the foreseeable future of re-inventing the wheel, rather let’s lighten it and make it turn more efficiently!
The engineers have taken to the piston design with a result that their weight is reduced by 10 per cent compared with the F60A and an increase in the air intake system by 17 per cent in volume by comparison has turned out a motor that has outstanding acceleration and longer legs at WOT.
The air intake tracks have been extended, tuned and then silenced by an air intake box. The ambient noise levels at all speeds is very acceptable indeed.
Yamaha is laying claim to being, at 120kg, the lightest-weight outboard in their class; lighter than all four-stroke and direct-injection two-strokes of similar horsepower. They tout their nearest competitor being 155kg in four-stroke and 145kg in two-stroke technology.
ON THE WATER
The Seajay with two crew achieved 60.95km/h at 6300rpm with a fuel burn of 24 litres per hour. This gave the rig 2.54km to the litre.
The Cruise Craft at the same revs maxed out at 54.45kmh with 23.60 litres being consumed with the average km/l being 2.31.
The best distance per litre for the Sea Jay was 3.64km at 3500rpm and 29.70kmh. This averaged out at 8.15lph fuel burn.
On the other hand The Cruise Craft’s best km/l was 3.20 at 4500rpm with an average speed of 36.95. The fuel burn was 11.55lph.
The test day saw three large adults aboard each of the boats and they performed admirably. Especially (and surprisingly) the Cruise Craft which would have weighed around 1100kg.
The F70A understandably did not have blinding hole shot on this hull but climbed onto the plane easy enough and could maintain its speed during hard turns without bogging down. And that’s where we were impressed; its torque output enabling it to stay on the plane given the boat mass and the horsepower attached, was very impressive.
The fact that these engines can swing the same props (K-series) as the F80 through to the F115 engines is testimony to the amount of torque coming through to the gear case which has a ratio of 2.33:1. And it gives the end user a wide range of props to better your boat’s performance.
Mechanical:4.5/5.0
On the water performance: 4.9/5.0
Value for money: 4.5/5.0
X-factor: 4.9/5.0
Specifications -- Yamaha F70A
HP: 51.5kW (70ps) @ 5800 rpm
Engine type: 16-valve SOHC in line four-cylinder four-stroke
Displacement: 996cc
Compression ratio: 9.4:1
Weight including prop: 119kg
Gear ratio: 2.33 (28/12)
Propeller: 13-5/8 X 14
Recommended retail price: $10,412
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