Hi can anybody give me an approximate of what fuel consumption to expect from a 15hp Kobota diesel pushing a 27ft 2.5 ton sail boat, I'm thinking about 1 litre per hour?
Any help would be appreciated

Within 10 seconds I found graphs on fuel consumption for that motor on google. In all different colours aswell.

Seriously would have taken longer to sign up to seabreeze.

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Akarua said..
Hi can anybody give me an approximate of what fuel consumption to expect from a 15hp Kobota diesel pushing a 27ft 2.5 ton sail boat, I'm thinking about 1 litre per hour?
Any help would be appreciated

How long is a piece of string?

What revs?

Boat speed?

Sails up?

current speed?

Exhaust size?

Beer supply?

Daylight or night time?

Colour of boat?

Ill say 1.2679 L per hour

Will depend on if you are going up hill or down hill.

^^^ it it is rough seas, its both up and down.

Cancels out to zero consumption.

My Kubota uses about one liter per hour pushing a 7 tonne 24 foot hunk of steel. It does so at varying speed and efficiency, that is dependent on current and wind conditions.

I am thinking of changing to a Kobota.

So

I realize there are variables but just motoring in calm seas and no current then I can work out current affect sail's affect swell affect, colour of boat and weather or not everybody on board had a **** before setting sail

Get a foil under it.

Less power needed when up and going.

Rough rule of thumb is a litre per hour per 10 hp for a diesel. that's regardless of the brand of diesel. A lot of boats are overpropped because the motor doesn't appear to be working hard enough to the owner, big mistake.. Overpropped will kill the motor. At full throttle the motor must be able to rev out freely to maximun revs. Bottman.

1 litre an hour is ridiculously over conservative.
diesels are more efficient but there is no mention on revs here let's say you had it idling at 900-1100 I'd estimate minimum 3 litres an hour at your 2000 revs likely 5+

And here I will explain why, it would be prudent to always have 30% fuel left based upon voyage let's say you fill your diesel tank all the way up, start motor and drive for 10 hours at 2000 revs you return to jetty and refuel it takes 50 litres excellent first my maths is perfect secondly you now have a weighted calculation for your ship at 10 hours of steam time.
( one hour will be insufficient to gauge usage)
so now you have established fuel consumption at revs.
it may of been a perfect day and your average speed was 10 knots so you did 100 nautical miles total.
Epic trip good work, now next time you go out the weather is terrible and you still need to travel 100 nautical miles but can only do 7 knots, well your going to do the same distance but burn more fuel so it's likely you may use 30% more.
This now becomes your average.
remembering that even on this bad weather day you want to have 30% left in the tank at least when you arrive back at port........
as an assumption i would start with the above figures and do a proper 10 hour steam preferably at full revs on a nice day with a full tank, it would be prudent at 3 hours in if you do not have large tanks to dip the tanks to ensure you have enough to turn around and get back in.

at idle a generic calculation in diesel motors is for every 50 hp you will use 10 litres so a 500hp idling for an hour will use 100 litres ( actually around 60 to 80) however again until it's proven in your specific vessel at a weight to power ratio you have 20-30% back up
sime motors at 500 hp will easily easily chew 100 litres in an hour+

Turbos , prop size , weather conditions, weight of vessel, Hull shape etc will all contribute.

Thank you for taking part in diesel consumption 101

next week I will cover navigation