MD11c: Fuel consumption

[alisdair4]

Although I have had my boat (Rival 32) for nearly 3 years, I have no idea of the average fuel consumption of her Volvo Penta MD11c. This is simply because I have never motored her any significant distance. However, I am now looking at quite a long trip this summer. Some of this, eg: through parts of the Caledonian Canal will be under motor.

Can someone advise the average fuel consumption for this engine at about 1600rpm?

 

[Searush]

If anything like my MD2B, it is 2/3rds of beggar all, or less. I'd allow 1/2 gal/hr, oh, err, ok, about 2l/hr. Why worry on a canal, there should be a few places to buy more.

 

[musarkie]

I have a MD11c with saildrive, and of memory it takes about 2.5 l/hr at 1800 rpm. This should give you a bit of a safety margin.My boat has a 100 ltr tank so I work on 40 hrs fuel.
regards
stuart

 

[alisdair4]

Thanks. It's the North Sea crossing after the Canal that I am concerned about. I think it unlikely that we'll have to motor for very long (even in July). However, I want to ensure that I have sufficient margin!

 

[Tranona]

The rule of thumb is 1L per 10 rated hp per hour. There is very little difference between engines. My Yanmar 1GM used about .75L and my current Volvo 2030 just over 2L. What, of course varies is the distance covered in relation to fuel used depending on the efficiency of your prop and the prevailing conditions (+tide if appropriate).

 

[Searush]

Just put a 25l plastic barrel somewhere so that you have some for the far end, where you may need to motor some distance to get into a safe haven.

I wouldn't expect many calms on a N Sea crossing, and even head winds would be pretty rare for the crossing too at a guess.

 

[alisdair4]

Fuel consumption

Tranona, thanks, I was sure that there was a "rule of thumb" somewhere!

All, thanks for your help.

 

[reeac]

The rule of thumb is 1L per 10 rated hp per hour. There is very little difference between engines. My Yanmar 1GM used about .75L and my current Volvo 2030 just over 2L. What, of course varies is the distance covered in relation to fuel used depending on the efficiency of your prop and the prevailing conditions (+tide if appropriate).

I've always thought that the rule was 20 bhp.hours per gallon of diesel and that's consistent with engine manufacturers' figures although they state as g./hp.hour or g./kWh. That's 4.4bhp.hour/litre - very different from Tranona's figure of 10. Of course you need to know how much power you typically take from your engine and that will depend upon the displacement of your boat, sea state, tidal flows and your own preferences. Personally I find that, based upon the 20 bhp.hour figure I seldom exceed half power in our VP2002-powered Sadler 29 and more usually use 6-7 of the available 18 bhp. That gives 3-3.5 hours per gallon. Stand by now for the bore glazing issue to be raised. In the specific case mentioned I'd bet on 2 hours/gallon.

 

[drawp]

Actual consumption.

I have a MD11d engine in my boat - 35ft overall weighing in at about 8 tons. The average consumptions for each the last 6 tanks of diesel when taking about 90 litres each time, were 1.94, 2.33, 1.70, 1.65, 2.21, 2.04 - all litres/hr. The 2.33 l/hr was when motoring for long periods at relatively high revs across Biscay and the 2.21 figure while punching down the Portuguese Atlantic coast. At around 1750 RPM, I would expect to get about 1.75 l/hr. Push it harder and the consumption will rise to over 2.0 l/hr.

 

[SHUG]

The bottom line is that for your engine you will get 3 to 6 miles per litre depending on the conditions.
I don't agree with the general rule of 1L per 10 rated HP per hour since I have found that it only applies when the engine is delivering full HP. With an 85bhp engine in a 43ft boat I found that at full bore in tough conditions, the consumption was indeed about 8litres/hr but in light conditions it was about 3L/hr as the engine was only delivering , say, 30bhp or less.

 

[alisdair4]

Draw,

Sounds like your boat is closest to mine in terms of weight and HP, so these figures are very helpful. What it tells me is that, with a 25g (Approx 100l) tank, and 40 litres of spare in cans, I should have no dramas even if I have to motor all the way from Lossiemouth to Thyberon!

 

[macd]

I also have a Rival 32, with a 28hp Beta. In flattish conditions motoring at 5knots I never exceed 2 litres/hour and usually nearer 1.5 litres -- perhaps slightly below drawp's figures, as you might expect from a lighter boat. Obviously this won't necessarily be replicated in your North Sea crossing, but if there's any sea running you'll be hoping the wind is proportionate in which case you'll probably be sailing.