What is the fuel consumption of a Hunter 310

[yotano211]

I am looking at a 2000 Hunter 310 as my 1st sailboat. I know the fuel tank size is 25
gallons. But I am looking for the fuel consumption of the 310 at normal cruising speed.

The engine is a Yanmar 18hp

[sailormed]

If you have the engine type number you can find the official Yanmar fuel consumption graph easily on the internet. My engine is a 3JH4E, but it is 39 HP. Find the engine type number and voila...

[StuM]

It depends on your "normal" cruising speed.



But in calm conditions at 5+ knots with a 28ft LWL and 4000 kg displacement?

I'd estimate you'd be using up to about 10 HP.
That would probably be around 3 litres per hour ( about 0.8 US Gallons per hour).


In adverse conditions or pushing faster than that it could half as much again.

[Snore]

Originally Posted by yotano211

I am looking at a 2000 Hunter 310 as my 1st sailboat. I know the fuel tank size is 25
gallons. But I am looking for the fuel consumption of the 310 at normal cruising speed.

The engine is a Yanmar 18hp

My SWAG on deliveries is 1/4 GPH/ 25 HP @ 21-2200. Most boats use less than that.

Unless you are doing some huge crossing that tankage should be good for a Hunter 31.

[StuM]

Originally Posted by Snore

My SWAG on deliveries is 1/4 GPH/ 25 HP @ 21-2200. Most boats use less than that.

Unless you are doing some huge crossing that tankage should be good for a Hunter 31.

1/4 USG/h is only about 1 litre per hour, which would only be using about 4-5 HP based on the common rules of thumb of .25 l/h/HP or 1 gph for every 20HP. I'd consider that dangerously low as a planning figure for the boat in question when talking about maintaining a "normal cruising speed".

[Island Time O25]

The fuel consumption rate for many makes of Diesel Engines can be found in a range between 0.380 & 0.450 lbs/hp hour; 172 & 181 grams/hp hour; 231 & 243 grams/kW hour. This does not represent a big difference in fuel consumption per power unit between most normal naturally aspirated diesel engines, while turbocharged engines are not significantly better. (c)

https://barringtondieselclub.co.za/t...-aspirated.pdf

Another very rough approximation as to the size of fuel tank relative to HPs of the engine is to have a bit more gallons then HPs. So 25gals for a 18HP engine should be plenty, unless you don't plan to sue your sails at all. I have a 32HP engine and a 40gal tank. A friend has a 75HP engine and 100gal tank. You get the idea.

[StuM]

Just to take it a bit further in simple terms, if you have to motor for some reason, your 25 US Gallons is probably good for 30 hours / 100 - 150 nautical miles in reasonable conditions.

[Boatguy30]

I've run a ton of hours on this motors. At about say 3000 rpm you'll be right about .6-.7 gal/hr. Great motors but not quite as fuel efficient as some other diesels

[Snore]

Originally Posted by StuM

1/4 USG/h is only about 1 litre per hour, which would only be using about 4-5 HP based on the common rules of thumb of .25 l/h/HP or 1 gph for every 20HP. I'd consider that dangerously low as a planning figure for the boat in question when talking about maintaining a "normal cruising speed".

We almost agree, that is why I quoted an rpm.

I’ve had this debate with owners. Then we run the boat at the lower RPM and prove out the better MPG.

[a64pilot]

It depends on how you define normal cruising speed.
Run it at 3000 RPM and it’s likely you will burn .7 GPH, run it at 2000 RPM and it’s likely you will burn half that amount, but your speed will be only reduced by a 1/3 or less.
AND, whoever is below won’t go deaf and be a nervous wreck listening to a motor screaming at 3000 RPM all day.

Once you accept that it is a sailboat, but sometimes your forced to motor and accept that you motor slow, your fuel burn will be low and at least as important your range will be greatly extended.
I have a longer waterline so my speed is higher, but to give an example 1800 RPM or so gives me with a 44 HP engine a fuel burn of about .7 GPH and a speed of 6.5 kts.
Increase to 2500 or so doubles my fuel burn and adds a kt to give me 7.5 kts. Run it wide open gives me 8 kts at 3400 RPM or so and I have no idea what fuel burn is but bet it’s at least 2.5 GPH.

People want to believe there is a sweet spot RPM wise where the motor is most efficient, the better educated ones can show you BSFC graphs to prove it, this sweet spot is usually pretty high in the RPM range, and they are correct, there is a small increase in engine efficiency, but it’s small, but more importantly it’s way more than offset by greatly increased drag at even slightly higher speeds.

This belief of the sweet spot goes across everything, there are whole legions of people who are convinced their cars get better fuel mileage at higher speeds, but they are incorrect

[yotano211]

Originally Posted by a64pilot

It depends on how you define normal cruising speed.
Run it at 3000 RPM and it’s likely you will burn .7 GPH, run it at 2000 RPM and it’s likely you will burn half that amount, but your speed will be only reduced by a 1/3 or less.
AND, whoever is below won’t go deaf and be a nervous wreck listening to a motor screaming at 3000 RPM all day.

Once you accept that it is a sailboat, but sometimes your forced to motor and accept that you motor slow, your fuel burn will be low and at least as important your range will be greatly extended.
I have a longer waterline so my speed is higher, but to give an example 1800 RPM or so gives me with a 44 HP engine a fuel burn of about .7 GPH and a speed of 6.5 kts.
Increase to 2500 or so doubles my fuel burn and adds a kt to give me 7.5 kts. Run it wide open gives me 8 kts at 3400 RPM or so and I have no idea what fuel burn is but bet it’s at least 2.5 GPH.

Thats a good fuel burn for the speed.

[Skreipen]

This is the fuel consumption for a HR31 at different rpm https://www.hallberg-rassy.com/filea...Ipropeller.pdf it might give you a clue

[psk125]

No one has asked about how many blades the prop has, what the size and pitch is, or whether it has been painted with antifouling. Each of these will have a HUGE impact on fuel consumption, not to mention how a 20-year old engine might have issues with rings, fuel injectors, or other things. If fuel consumption is the key concern, they need to each be taken into account. If fuel consumption is the key concern on a sailboat, however, THAT would be a concern.

StuM’s advice on range/running time is probably the most useful and sufficient; your mileage may vary. To Jedi’s point, a question about replacing tired sails might be more pertinent to this kind of purchase.

[Pizzazz]

I did this exercise for my Hunter 31, 2GM20F, with a Martec folding prop. I assume 10 nmpg for planning purposes. And for reference, the 2GM series burn about 220 g/hp/hour.

[hamburking]

One litre of diesel fuel per hour. More at WOT. Less if you throttle back to 4 knots. That's a british litre, not an american liter.