Yanmar fuel consumption

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brians

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I have a 4JH3E, 56hp, engine that I am still getting to know. Can anyone advise the approximate fuel consumption at say 2000 and 2500 rpm? I would like to ascertain the range of a full tank of fuel.
 
That depends on how much power the engine is producing. Which will depend on your boat, the prop size, sea conditions, whether the hull is clean etc.
 
RichardS said:
Probably around 6 litres per hour at full power and half that chugging along at 2000 revs would be a reasonable basis for estimates. :)

Richard
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If it was actually putting out 56hp, you'd expect about 12 litres an hour.
But in flat water at 2000 rpm, 3 litres an hour sounds as reasonable as any other guess.
 
As said before, it doesn't depend only on the revs, but also on how much power is the engine delivering at the particular revs. Depending on the gear and prop, the engine my not be always delivering the full power corresponding to the particular revs. For some approximate calculations you may use the performance curves supplied by the manufacturer, but you have to accommodate for the possible difference mentioned above. As I found out by experimenting with my 3 cyl turbo Yanmar, they can be significant. If you want a really accurate answers, the best way is measuring it using a temporary fuel feed from a calibrated bottle. That is what I've done eventually; it is not that hard.
 
The answer depends also upon why you want to estimate range. Are you planning a long distance cruise where fuel stops need to be factored or simply for interest? There are many variable as previously pointed out. During the course of an average season, many of the conditions will likely be seen. I’ve just done a 5 day cruise, one day I used the engine at 1400 to provide a bit of help to reach a tidal gate. Another day I didn’t like beating into a F6 so motored into it. Massive difference in fuel consumed in these two situations.

I’d use 4.5 l/hr x 90% of tank capacity and always carry 2x10 litre cans as spares. Log hours and fuel added each time you’re on a fuel berth and develop a long term average over your cruising style.
 
Hi

We have a 4JH3ME (what's in a name?) in a 41 foot Dehler deck saloon. We rarely thrash the engine (normally running around 1800 rpm) and over the years find that 3 litres per hour is a good working average.
 
It's not even particularly engine-specific. Most use much the same technology to turn fuel of the same energy content into work. Our 50hp Beta uses much the same as others have reported at steady cruising revs on a 43-footer.
 
syfuga said:
Hi

We have a 4JH3ME (what's in a name?) in a 41 foot Dehler deck saloon. We rarely thrash the engine (normally running around 1800 rpm) and over the years find that 3 litres per hour is a good working average.
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so would that engine be delivering around 30hp at those rpm
 
Old Harry said:
so would that engine be delivering around 30hp at those rpm
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There's no simple way of knowing. The power graph would show whether it was capable of producing 30hp at those revs. But it was probably producing substantially less, because less was needed to propel the boat. Think of a car held at specific revs in top (or any other specific gear): consumption would vary depending on whether it was on the flat, uphill, or downhill. Ultimately you'll reach an incline at which the car can no longer maintain that rpm. (Many modern cars can display the instantaneous fuel consumption to confirm this.) Most of us are familiar with the effect of fouling, where more throttle is needed to maintain the same rpm, and fuel consumption increases as a result, even though that rpm also produces less boat speed.

Edit: hence lw395's observation, which popped up whilst I was typing.
 
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