Does anyone have an idea as to how much running time I would have on a full tank of diesel in the 31' Hunter?
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The 3GM?
You should be able to cruise and expect .5 to .6 gallons per hour. This in good conditions, not bucking currents and waves and headwind. So if you plan for .75 gph you should generally be safe.
You should be able to cruise and expect .5 to .6 gallons per hour. This in good conditions, not bucking currents and waves and headwind. So if you plan for .75 gph you should generally be safe.
Rough Calculation
I agree with Ed's estimate. According to the specs on this website, a H31 has a 20 gallon tank. That gives you 26.6 hours of run time (20 divided by .75). Assuming you are cruising at 6 knots, that translates into about 160 nautical miles (6 times 26.6). If you have more accurate numbers you can get a better answer -- it's good to keep a ship's logbook for recording this kind of info (among other things like when you last changed your fuel filters). My guess is you can probably go close to 200 nm -- best to be conservitive in these matters.
I agree with Ed's estimate. According to the specs on this website, a H31 has a 20 gallon tank. That gives you 26.6 hours of run time (20 divided by .75). Assuming you are cruising at 6 knots, that translates into about 160 nautical miles (6 times 26.6). If you have more accurate numbers you can get a better answer -- it's good to keep a ship's logbook for recording this kind of info (among other things like when you last changed your fuel filters). My guess is you can probably go close to 200 nm -- best to be conservitive in these matters.
One Thing to Consider
Your fuel pick up position will never allow a complete draw of the fuel in the tank. Allow about a 5% factor for that, which would equate to about a gallon of fuel on a 20 gallon tank. For some reason I thought that the 31 had a 25 gallon tank but check the specs on this sute for the correct information.
Your fuel pick up position will never allow a complete draw of the fuel in the tank. Allow about a 5% factor for that, which would equate to about a gallon of fuel on a 20 gallon tank. For some reason I thought that the 31 had a 25 gallon tank but check the specs on this sute for the correct information.
one more tidbit
My H31 came equipped with a 2GMF not a 3GM. I believe some version of the 2GMF is standard in these boats.
My H31 came equipped with a 2GMF not a 3GM. I believe some version of the 2GMF is standard in these boats.
Our tank was smaller than 20 too!
You may want to calculate the size of the tank, but I think ours was only 18 gal. We have always run the engine at 2800 when we were making a run for any distance and have never seen fuel consumption that low. We have always averaged .75 - 1.0 gph. I am sure that there are many things that influence this. You also probalby do not know if someone has messed with the fuel pickup unless you have owned the boat since it was new or have run it out of fuel. So, my advise to you would be to plan on refueling between 12-15 hrs. Then you can do your own calcs. and that is correct the '31 came with the 2gm.
You may want to calculate the size of the tank, but I think ours was only 18 gal. We have always run the engine at 2800 when we were making a run for any distance and have never seen fuel consumption that low. We have always averaged .75 - 1.0 gph. I am sure that there are many things that influence this. You also probalby do not know if someone has messed with the fuel pickup unless you have owned the boat since it was new or have run it out of fuel. So, my advise to you would be to plan on refueling between 12-15 hrs. Then you can do your own calcs. and that is correct the '31 came with the 2gm.
Fuel Burn
I checked fuel burn on a recent 7 hour motor with the H31 with a 2GM. Flat water, no winds 6 kts, 0.67 gph (US gallons) I'll use 0.75 in the future and also carry 5 galls "just in case"
I checked fuel burn on a recent 7 hour motor with the H31 with a 2GM. Flat water, no winds 6 kts, 0.67 gph (US gallons) I'll use 0.75 in the future and also carry 5 galls "just in case"
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