Engine

[Andrewcook]

As there a few good Diesel  Engines fitted in Boats which one does uses less Diesel?

[Smoggy]

Not mine that's for sure.

[annv]

Hi Andrew how long is a piece of string!! A modern Nanni/Kubota is very fuel frugal, A BMC for an old engine are also frugal but can be a hard starter. Why do you want to know? are you going to buy a new engine, Another factor is how you drive it, a small engine driven flat out will use more than a larger engine engine driven on low rev's. also what type of fuel can make a difference. John

[William92]

It's a whole can of worms, you'll also be wanting to know about prop size for the engine you choose.

Fuel consumption is a tricky one, litres per hour is only part of the story (try running at an rpm that gives you 3mph through-the-water against a 3mph tide, you'll burn very little fuel but you'll burn an awful lot compared to the boat moored alongside you 😄). Turn the other way though and you'll be making an excellent 6mph on very little fuel consumption indeed!

Strictly speaking, you get best efficiency (fuel into BHP) typically around 70% engine load (there are graphs somewhere), which is hard to achieve. If you are absolutely dead-set on maximum fuel efficiency (I make no claim of the cost effectiveness of the following...) then a hybrid drivetrain (Nanni has a little pancake motor that slots in between the engine and the output, I presume it's clutched so it can decouple from the engine, as an example) would be an interesting place to look into. They can add artificial load onto the engine to charge batteries, to force it to run at a more economical engine load for any given engine speed (rather than trying to maintain a specific speed through the water and upsetting everyone moored by the bank), and later on you can switch the engine off and use the motor to blissfully glide across a broad in near silence, etc.

The hire companies will have thousands of hours on Nanni engined boats, both hybrid and non-hybrid, and they could possibly give you a comparison of the average fuel efficiency if you ask them really nicely? (nb. their hybrids also might plug-in at the bank, again, using less fuel, but at what cost?)

How many hours are you using the engine for in a given year, how much fuel are you trying to save, etc - also questions to ask yourself.

[MargeandParge]

Thanks for a great reply William 92. Me and Ole Marge will probably stick with the one we have as it would take a century to get our money back to save 10 litres of derv. However  if you could guarantee we had enough time left to make a successful investment we would consider. We think that you have answered all Andrews questions very well. 

Kindest Regards Marge and Parge 

[Andrewcook]

Hi William 92 & annv  thank you both  to this my very interesting attical 

[Smoggy]

I believe these are supposed to be good on diesel, crap on direction though...

[YnysMon]

Moonlight Shadow had a new engine a three years ago, but we only got the prop checked at the start of last year, which resulted in a new prop being installed. Ive been keeping a record of our fuel consumption/costs for the last couple of years, and have noticed a marked reduction in fuel consumption since we had the prop changed. 

[ChrisB]

Hull design, waterline length and beam have a bearing on consumption. Comparisons are notoriously difficult to make.

[Vaughan]

I agree with ChrisB. It also depends a lot on the prop.

A long boat will normally use less than a short one, at the same speed.  We saw pictures on another thread of Broad Ambition and a Safari 25 cruising together at the same speed.  The difference in wash was remarkable!

In France all our boats have hour meters, so I was able to keep records of the number of hours a boat cruised in a week, compared to the amount of fuel we topped up with afterwards.

The most economical average was the Perkins 4108, at a consistent 1.6 litres per hour.

We didn't have any BMCs.

The Nanni 4220 used between 1.9 and 2.5 litres, depending on the boat - and the hirer!

I noticed that a Clipper, with the same hull and engine as the Crusader, used a lot less fuel.  The difference here was the prop.

Speed makes a great difference.  The Nanni 5 cylinder, when on trials in a new boat, was using just over 7 litres/hour at 2400RPM, with a 22X18 prop.

Speed limits in France are more than the Broads - about 7MPH, so on the north rivers you can expect to use less than these figures.

[Cheesey69]

Agree to all of above.

1.5 bmc 35 foot bermuda flattie.

Speed is the greatest cost to diesel

As an experiment, I just cruised everywhere at 4 mph, 1500 revs adjusted to maintain 4 mph even down south and the savings was huge.

I was working on 9 miles per gallon (4.5 liters per gallon) this works out about 1.8 liters per hour but by taking it easy im getting much less. 

The important bit, clean hull just anti-fouled and a recon injector pump

[Andrewcook]

All this is very artical as to Prop Broad Ambition has a Four Blade propeller and a very good Prop to match as think this helps the Boat move very nicely on Fuel Consumption?

[YnysMon]

I also think that planning cruises around the tide table, so as to minimise time fighting against the tide, can save a huge amount of fuel…especially down south. 

[Smoggy]

 

50 litres of diesel per hour, don't ever moan about fuel consumption on the broads....

But it's fun and you get to the pub much quicker.

[Andrewcook]

Maybe for Criff to get there  before closing time lol

[Smoggy]

4 minutes ago, Andrewcook said:

Maybe for Criff to get there  before closing time lol

If Griff is on my boat it's his round at that fuel bill.

[NeilB]

1 hour ago, Smoggy said:

50 litres of diesel per hour, don't ever moan about fuel consumption on the broads....

But it's fun and you get to the pub much quicker.

Amateur!  See the highlighted figure from the last sea trial I carried out at work, that’s the total for both engines.

Next up is Griff with the fuel burn from HMS Newcastle