Sealine F37 Fuel Consumption

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shanwick

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I'm fairly new to the engine concept having converted from cloth last year so bear with me.

I have an F37 with Volvo D4-260 engines and wondered if anyone with the same boat has consumption figures at various RPMs?

Is there a "sweet spot" for this boat?
 
Not really relevant data.

The GM37 is lighter, leaner and on outdrives. It is ackowleged to be one of the most efficient hulls in its class.

Nowt wrong with an F37, but the data will be completely different to that.

I would expect the F37 to use around 3l/nm at the absolute best with D4s. Add a bit of excess weight, sea state or slimy botom and its probably getting on for 4l/nm
 
Its only relevant for consumtion pr h! If (I dont know the top speed for this boat just assuming 28 knots) the boat is doing 28knots at max speed the consumtion is 3.7l/nm. If you reduse speed 10% you reach approx 25knots
and 38-40l/h pr engine giving 3.0-3.1l/nm. Redusing speed down to 80%
gives 2800rpm and 21-22knots and 28l/h pr engine!

But!
Below froude volume number 3.2 the boat is not a true planning hull!
Thats below 26knots on this! So at 80% engine speed the boat is propably is running slower giving a higher consumtion! The consumtion at 2800rpm can vary from 28l/h(2.5 propeller curve) to 43l/h (max torque) and the speed can be from 15 -21knots! so worst case 5.5/nm Best case 2.6l/nm! My guess 4l/nm!

To get it lower than 28l/nm at 2800rpm you need a rope conected to a fast ship! (Queen Mary?)

Anyway! This engine might be small to for this boat! Depending on semi displasement behavior!

When you know the engine speed/boat speed its easier to calculate!
 
The D4s should be more efficient than my KAMD300s. I get about 1.1 nmpg at around 25 knots in my F37. She will plane down to about 14 knots, but over a few thousand miles the consumption doesn't seem to vary dramatically with speed - mind you when I'm crusing slower, the sea is usually bigger.
 
The Windy test sheets are very interesting although probably a very differeny hull shape and I assume the Widy 25 has Outdrives which are somewhat more efficient than shafts on the Sealine F 37.

Its a shame the windy results dont show 1700, 1800, 1900 and 2100 rpm.

On the F37 which cruises comfortably at 25 knots and planes I assume at 14 or 15, I would assume the most efficient is 18 or 20 knots.

If you are going from A to B the thing that matters for efficiency is Litres per Nautical Mile and not Litres per Hour.
 
The performance tests was only for comparing D4 against KAD300!

To find the optimum speed can be difficult! But i think your right about 20knots!

I do agree its the l/nm that interesting!

That was the point with the links. All engines had the nearly same l/nm at the same boat speed!

At 30knots KAD300 0.97l/nm D4 260 0.94l/nm D4 300 0.92l/nm

At 40knots KAD300 1.16l/nm D4 260 1.16l/nm D4 300 1.07l/nm



That means that the consumtion JohnRob is reporting with his KAD300 is the one you should expect!

1.1nm/gallon or 3.4l/nm at 25knots on this Sealine 37 boat!
 
Weight of a boat makes a big difference.

Fouling of a hull makes a big differnce.

Weight of engine makes a very small difference.

Providing either engine is not operating at between 95 to 100% of power small difference.

D4 against KAD 300 very small difference.

I used to work on 186 gramms per kilo watt hour, the secret is knowing how many kw are used at any boat speed.

Suppose the Kad 300 and the D4 are both running at 20 knots with a clean hull and same boat and same weight I would say the fuel consumption per nm is within 3 to 5%.
 
The D4 260 is using 230g/kwh at full load! At 3000rpm its using 214g/kwh!
Most small engines are in this range!

186g/kwh you are in the medium speed range engines!

Knowing the kw!

The power curves for a fast boat is in average a Full power* (N/Nmax)^2.7 in average on a lot of tests! But i have seen curves varying from 2.5 to 3.5!

This means at 80% engine speed most engines is at 55% power.

This is only in areas where you have pure dynamic lift or true displasement mode!
 
Multiply by two for two engines - There's nothing special about an F37 that wil produce dramatically different figures.
I'd expect a good cruise speed to be 20-21kts or thereabouts.
Assuming 3000rpm gets 20kts, 70L/hr total = 3.5L/Nm = 1.3 Mpg

d4-260.png
 
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put it in simple terms I have a 40ft LOA not flybridge its 8.5t without the wife's shoes, I have the same engine and the fuel consumption gauge says I use around 30lt per hour per engine cruising at 22 knt, you should be about the same maybe a touch less.
 
I guessed you might be. Your 1.66 mpg is unlikely to be achieved by a similar boat with the same engines but running on shafts. I would guess somewhere between 1 and 1.2 mpg would be the norm for an F37
 
We get around 1.3mpg from KAMD43P's (230hp) so I wouldn't expect much different from the D4s. The fuel consumption on this boat is very dependent on loading and fouling, BTW. A clean bum and getting rid of all the extraneous crap you tend to accumulate makes a huge difference.
 
The difference of a clean hull to one that has been antifouled but not cleaned for 12 months is around 30% more fuel at 22 knots. See MBM last year.
 
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