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Discussion Starter · #1 ·
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.
 

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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
 

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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.
 

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Discussion Starter · #4 ·
Sounds like I'm in the right ballpark--I really had no idea what the approximation is: thanks a lot for the validation.
 

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2QM Fuel consumption

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.
 

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Hull Speed vs RPM

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....
 

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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....
 

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+1 on the responses

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
 
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