When Yamaha released their lightweight 70hp 4-stroke outboard the F70A, it gave every indication of being a real game changer. Here for the first time was a 70hp motor weighing in at not much more than equivalent 2-strokes, and significantly less than 4-stroke competitors. Three years on it’s fair to say the F70A has delivered on everything it promised. Super quiet and smooth running, it runs on the proverbial sniff of unleaded, while being as kind to the environment as we expect in this day and age. What a pearler of a motor. The F70A, to put it bluntly, left the opposition playing catch up, and by and large, it still does in many respects. No-one (as yet) has produced a direct competitor but, sales folk being sales folk, you sometimes hear that if the F70A has a fault, it’s that its comparatively small displacement leaves it somewhat short on (comparative) “grunt.” This line of thought makes sense when you consider that the F70A’s displacement is 996cc as opposed to Suzuki’s DF70 (a motor I mention not only for comparison’s sake as another “70”, but as a similarly quiet, smooth, and fuel efficient one) which displaces 1502cc. Honda’s 70 is 1496cc and Mercury’s 70, 4-stroke is a whopping 1732cc. Even Evinrude’s E-Tec 75, a direct injected 2-stroke motor widely admired for its “grunt”, displaces 1296cc. So there may be some validity to this opinion, even when filtered through that great leveller of such: common sense. The 670 Bar Crusher seen here was set up by Brisbane’s Stones Corner Marine for a PNG client who wanted the security a twin installation offers, for all the obvious reasons. It’s a utilitarian fit out, apparently destined for a long life of hard fishing but nevertheless Bar Crushers are solidly built, and on a trailer it weighs in at about 1.8 tonnes. Subtract a couple of hundred kilograms for the trailer, and you’ve still got a pretty hefty 6.7 metre plate tinny which, with Bar Crusher’s 22 degree deadrise, is going to take some getting out of the water. The hull is rated for a minimum of 150 hp, and given the added drag of the extra leg inherent in twin installations, it figures those “little” 70 hp 4-strokes are going to have their work cut out; although the additional torque available from two motors instead of one should compensate to some extent, as twin installations tend to do. This is clearly one of the more interesting tests I’ve done and I must admit more than usual curiosity when I opened the throttles as we cleared Brisbane’s Manly Boat Harbour. To my surprise, and in defiance of popular opinion and commonsense alike, the big Bar Crusher eased onto the plane and powered away with no apparent effort. Pulling the throttles back to check this sure indicator of torque available, or lack thereof, down to 12kph (2200rpm), it stayed solidly on the plane. Easing back even further, the prop wash met our transom as over the ground speed passed through 11kph. At 4000 rpm we were motoring along at 38kph, while fuel consumption edged past 20 l/hr to a whole 20.3. At 4500, still reasonable cruising revs, our speed had increased to 42kph and fuel consumption a whopping 23.9 l/hr. WOT at 6300 rpm produced a top speed of 57kph. Not too exciting perhaps, although about what you’d expect given the added drag from two outboard legs. However you look at these numbers, they speak volumes. As for popular opinion and common sense, what do you reckon?


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