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Old 30 May 2016, 13:44   #1
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Country: UK - England
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Fuel consumption 8hp Yamaha..

Hi all

I'm running a Yamaha 3.1m STI with a Yamaha 8hp 2 stroke o/board and I'm trying to work out endurance when using the Yamaha 25l fuel tank.

I'm thinking about 4l/hr at full throttle.

Anyone care yo offer opinions and/or a more expert/scientifically calculated figure..?

All comments welcome!.

Ian
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Old 30 May 2016, 14:07   #2
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Rule of thumb is that a two stroke uses 1 us gal (3.8 L) per hour running at full throttle for every 10hp. So you should get 8hrs+ out of a 25L tank.
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Old 31 May 2016, 02:58   #3
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Many thanks for that information. Sounds as if I'll have plenty of fuel in the tank for days out, without requiring extra cans.

Another concern alleviated!
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Old 31 May 2016, 04:23   #4
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Of course makes/models will differ but as a rough guide I always keep this link handy... a consumption guide from Tohatsu for 2 & 4 stroke 2-250hp. You'll see for the 8hp it has a figure in the same ballpark as Poly's rule of thumb...

Tohatsu Outboards - Fuel Consumption

Also this chart is interesting... it's a chart of speed vs fuel consumption for my 20hp. OK it's a 4-stroke and twice the capacity of yours so the actual figures don't matter but it is interesting to see the speed sweet spot to achieve low consumption...

SUZUKI DF20A Lean Burn EFI (scroll right to the bottom)

The very worse range was at 5kts.... even worse than flat out at 21kts.... and the best at a 13kt cruise.
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Old 31 May 2016, 05:56   #5
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Poly's rule is one I've always used but I'd go with proper UK gallons, ie 4.5 per hour and be a bit more pessimistic. All depends what you do in that hour so NM's covered is the more important criteria but my average is 1.8nm per litre for a 15.
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Old 31 May 2016, 06:09   #6
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all the info above sound.
but i will say always have enough fuel to get home if the s--t hits the fan you might have a run home at displacement speed due to a damaged boat, prop, etc possibly picking a longer but more sheltered route. just to think about.

cheers
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Old 31 May 2016, 10:28   #7
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Quote:
Originally Posted by jeffstevens763@g View Post
all the info above sound.
but i will say always have enough fuel to get home if the s--t hits the fan you might have a run home at displacement speed due to a damaged boat, prop, etc possibly picking a longer but more sheltered route. just to think about.

cheers
Or have a mental plan on where you can divert to for a refill, or even to catch a bus/train/taxi/hitch back to your car.
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Old 03 June 2016, 22:27   #8
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Quote:
Originally Posted by Flamair View Post
Hi all

I'm running a Yamaha 3.1m STI with a Yamaha 8hp 2 stroke o/board and I'm trying to work out endurance when using the Yamaha 25l fuel tank.

I'm thinking about 4l/hr at full throttle.

Anyone care yo offer opinions and/or a more expert/scientifically calculated figure..?

All comments welcome!.

Ian
I own the 8hp Yamaha 2stroke and use a 6gallon tank. You will have a hard to going through a full tank of gas in one day. I have yet to burn through one. And have ran longer than anyone would ever want to sit in a 310 inflatable.
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Old 04 June 2016, 07:45   #9
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That's very useful chaps.. much obliged.

Gwozhog -how do you find the 8hp copes with 2 adults aboard and limited kit, in terms of performance? Mostly I'll be using the outfit on lakes and rivers with the odd foray onto the briny..

Ian
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Old 04 June 2016, 10:00   #10
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you will plane fine with 2 heavy adults and gear no problem whatsoever. Three heavy adults and it won't happen. If you have your chance to get your hands on a clean 8hp Yamaha 2stroke I would pick it up quick. I have had me at 190 pounds and my father in law at 275 pounds and my Achilles jumped on plane no problem. We averaged about 15 mph top speed.
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