• Jun 23rd 2008 at 1:49PM
  • 5
It's not often that consumers choose a V8 engine for its low fuel consumption, but that seems to be exactly what is happening with the Yamaha F350 outboard motor. This sixty-degree engine is a rather high-tech design, featuring 32 valves and double overhead cams to produce some 350 horsepower at the prop shaft. One reason cited for its ability to save fuel is that the engines don't need to work as hard as smaller, high-strung engines.
According to Shane Kearns, who operates a water taxi in Australia, "Over the 35 engine hours clocked so far I have nearly halved my fuel bill with the twin F350 outboards returning a combined 31 liters per hour across a range of harbor conditions and boat loads. I originally thought my fuel gauges were wrong until I started closely monitoring my fuel intake." When first built, his boat featured twin two-stroke engines, which were later replaced with Yamaha four-stroke outboards. His latest F350s not only reduce fuel consumption but also provide additional speed and power, things which don't normally go together.

[Sources: Yamaha and Gizmag]

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    • 1 Second Ago
      • 7 Years Ago
      There are also major savings to be made by switching out two smaller engines for one bigger engine. I've heard of many people swapping out twin 150-200 horsepower engines for a large single. That not only saves on fuel, but also purchase and maintenance costs.

      Twin engines on a boat don't scale power the same way a single does. The extra propeller and lower unit (as well as extra weight) all contribute to inefficiency. Thus, a 350hp single engine can usually replace twin 200's.

      The larger outboards also can be used on bigger boats. It used to be impossible to economically power a 26+ foot planing hull with outboards. Now that's almost the norm. Outboards offer a number of advantages to owners and operators over inboards and sterndives. They're much less maintenance intensive than sterndrives, easier to maintain with less downtime than inboards (the less downtime is because it's possible to keep a complete spare engine and swap it out overnight, and it's also not located at the bottom of a bilge), and efficiency gains over inboards.

      The three main ways manufacturers are going after the large outboard market can be summarized with Mercury, Yamaha, and Evinrude. Yamaha simply goes for huge displacement. Mercury now supercharges it's large outboards. Evinrude has developed very high tech 2-stroke engines that utilize a very interesting direct injection system. The injectors are essentially speakers and can inject fuel many times per revolution. The oil is also very precisely metered, to the point where some of their 2 stroke engines actually use less oil over time than 4 strokes!
      • 7 Years Ago
      I suspect that the duty cycle of a motor in marine applications makes the difference.
      • 7 Years Ago
      Advent- I doubt they use "speakers". Perhaps pizeo injectors, which are common place on new diesels as well.
      stevefazek- any car going 150mph will use more fuel than 15mpg. you're correct about boats though.
      • 7 Years Ago
      so his average fuel consumption runs about $50. per hour. and thats considered a savings - wow - I'm gonna stick to paddling
      • 7 Years Ago
      Thats pretty damn impressive. My 95 HP merc 2 stroke burns 6 gallons an hour.

      A boat burns alot more fuel than a car its just like a plane. a car can reduce throttle and cruise and coast. A plane and boat are constantly fighting much higher drag levels.

      Even a Cesa with only 150HP or so burns 10 gallons an hour at only 150 MPH
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