Yanmar 2QM15 fuel consumption?

[30Irwin]

Hello: does anyone know what the fuel consumption is for a 2QM15? My new old sailboat doesn't have a fuel sensor; I could figure it out over time measuring engine hours against each top up, but maybe someone's already got the number. I cruise at about 2100 RPM.

The previous owner says he got about 70 hours of service from one tank. Going from 35 US gal tank to litres per hour I estimate 1.9L/hour. Does this sound right?

I welcome any thoughts-thanks.

[scottyt]

my 1 gm is slightly over a pint an hour by the specs, but i think it runs closer to 2 pints. maybe due to age or the fact that right now the head is being rebuilt. i would guess its close to twice the fuel use as my 1gm, so in reality its probably closer to 1/2 gallon an hour.

if you really want to know, for real rig up a one gallon gas ( i know diesel fuel ) can to the fuel input and return and run it until you use a 1/2 gallon

[catamount]

Originally Posted by 30Irwin

The previous owner says he got about 70 hours of service from one tank. Going from 35 US gal tank to litres per hour I estimate 1.9L/hour. Does this sound right?

Yes, that's pretty close. I use the figure of around 1/2 gallon (US) per hour at my moderate cruising speed (no tachometer). Yanmar specifications (you do have the factory Service Manual, right?), though, actually suggest a little higher fuel consumption, around 0.7 gallons (us) per hour at full power.

[30Irwin]

Sounds like I'm in the right ballpark--I really had no idea what the approximation is: thanks a lot for the validation.

[flatracker]

I had one of these engines in my previous boat. You can burn 1/2 gallon per hour, but have to really run it hard to do that. But if you use that figure, you should be safe.

[roline]

The rule of thumb that I've used is that you have 18 hp-hrs in a gallon of diesel. For a 2GM20 turning 2800 rpm with a 14dx12p prop cruising @ 6.3 knots, I burn just over a gallon in 2 hrs. (about 9hp)
If I run at 3200 rpm, I burn about an additional 1/2 gallon without much improvement in hull speed. (about 14hp).
See attached graph....

[catamount]

Originally Posted by roline

The rule of thumb that I've used is that you have 18 hp-hrs in a gallon of diesel.

The 2QM15 is rated at 14 horsepower, so 14/18 = 0.777 gallons per hour, which is pretty close to Yanmar's spec for the engine. Just some confirmation of your rule of thumb....

[DrB]

My 3GM30F Yannie, burns on average about 0.5 to 0.7 gallons an hour depending on RPM.

I think a safe number is 0.7 gal an hour for your purpose.

DrB

[30Irwin]

Excellent feedback from all; thanks again.

[Selkirk]

Rule:
Diesels burn about 1 gal/hour per 20 HP developed.
Gasoline burners use 1 gal/hour per 10 HP developed.