Yamaha yesterday released a 70hp four-stroke outboard that is both lighter and more powerful than all competitors in its class – including DI two-strokes.
The long-awaited F70A is a stand alone model which shares no interchangeable components with similar capacity engines. Based on an inline four-cylinder 996cc block, the F70A weighs in at only120kgs and boasts a power to weight ratio of 70hp per litre. In comparison, its nearest four-stroke competitor, Suzuki’s DF70, weighs 155kg and has a horsepower per litre rating of 47. Evinrude E-TEC’s 75hp is the closest overall competitor in power terms with a ratio of 58hp per litre, although the DI two-stroke loses out in weight at 145kg.
According to Yamaha national sales and marketing manager Brett Hampson, the F70A completes Yamaha’s mid-range line-up by slotting in between the popular F60 and the 80hp model. The 80 is based on Yamaha’s 100hp four-stroke and is too heavy for many tinnies and small fibreglass boats.
The F70A is targeted at the key 4.8-5.5m boat market, and is ideal for hulls weighing less than 680kgs.
Interestingly, the F70A is expected to take sales away from the successful F60, currently a top seller for the Japanese motor giant. Hampson says Yamaha expects the F70A to outsell the 60 by up to 2:1.
According to Yamaha technical spokesman Dan Power, the company has trimmed fat in key areas of the engine’s design to keep the weight down to 120kg (119kg sans battery cables). The engineers responsible for the new F70A appear to have followed the lead of Yamaha’s motorcycle division by incorporating high performance engine componentry in the form of lightweight pistons and valves (now four per cylinder, the F60 has two per cylinder), a stronger and lighter mounting bracket, and a lighter engine cowling.
A single throttle valve and intake manifold with separate chambers feeds each cylinder with fuel as required. Actuation of the engine’s intake valves comes via a new and innovative single rocker arm arrangement.
Typically, the new outboard boasts much of the niceties sported on other Yamaha four-strokes such as ECM micro-computer engine management, multi-point fuel injection, variable RPM adjustment for easier trolling speed adjustment, and a 2.33/1 final gear ratio. The latter feature makes the F70A compatible with Yamaha’s K-series propellers as used on Yamaha’s 80-115hp models.
The F70A also carries innovative features such as water separator with water sensor and an ignition knock sensor that automatically adjusts ignition timing for optimal running and to avoid engine damage when low octane fuel is detected.
Buyers also get the choice of three types of instrumentation including standard analogue gauges, digital LAN gauges or digital multifunction readouts – standard gauges will be supplied at no extra cost as part of the standard F70A engine package.
Also introduced with the F70A, and to be available on Yamaha engines from 2010, is the engine immobiliser, YCOP. Working much the same as a car’s keyless remote entry, YCOP prevents engine starting.
Fisho had a chance to sample two pre-production versions of the F70A – the only two in the country – at yesterday’s launch. One engine was fitted to a Sea Jay 4.85m Haven Sports, an open alloy dinghy, and the other to Cruise Craft’s new model Explorer 4.85 fibreglass cuddy cab.
A couple of test runs on the Brisbane River yesterday confirmed Yamaha’s claims of having lessened the holeshot performance gap between four-strokes and DI two-strokes – although in Fisho’s view DIs still have an edge in seat-of-the-pants instant acceleration.
The F70A is eerily quiet at idle. Noise levels naturally rise as revs climb and the engine gets down to achieving its 6300rpm maximum – a rev limiter cuts in at 6400 rpm. In Fisho’s view, the 631kg fibreglass Cruise Craft performed well with the F70A but when loaded to full capacity may be better served with its max power rated 90hp outboard. Three up at the F70A launch, the Cruise Craft climbed out of the hole without fuss with the engine pushing the ‘glass boat smoothly along to its maximum of 30.2 knots (56km/h) @ 6400rpm. The motor was fitted with a 14″ x 13 5/8″ K-series alloy prop.
In contrast, the Sea Jay performed the same run effortlessly, with sparkling holeshot performance that suggests the lighter (501kg) boat represents the round-about ideal hull match for the F70A. It certainly highlighted the engine’s strong midrange power – especially from around 4500rpm through to 5000rpm at where the motor emits a notable growl before smoothly climbing to maximum revs.
Three remote throttle arrangements are available for the F70A to suit different boat styles: standard throttle, concealed side throttle control and binnacle mount. The throttles on both test boats offered easy, light operation with good feedback in both forward and reverse modes.
Buyers of the F70A will have the choice of 20″ (F70AETL) and 25″ (F70AETX) shaft lengths to suit different transom heights. Tiller controls are also available, in 20″ shaft length only.
Yamaha expects production models of the F70A to hit showroom floors in mid-June. At this stage recommended retail prices are unavailable.
For video footage of the new F70A see below.
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More information at: www.yamaha-motor.com.au
