Fuel Burn and Range (How far can you go)

I have enjoyed the how slow can you go thread and it made me realize I am really not sure but I am going to add pure idle to my graph.

I have 3 tanks total 845 gals the range is with a 10% buffer

Twin Volvo TAMD 61As

It all depends on how much I want to spend!

I manage about 5gph with the generator running which gives me a theoretical distance of 528nm at 8kts.

I can bump it up to 17kts and it drops to 230nm.

k9medic said:

It all depends on how much I want to spend!

I manage about 5gph with the generator running which gives me a theoretical distance of 528nm at 8kts.

I can bump it up to 17kts and it drops to 230nm.

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I use the how far can we go more for fuel purchase at what stop along the way has the best fuel price

well..

I would venture to say that almost all coastal cruisers have enough fuel capacity to go anywhere in North America

The furthest place that I know of in the United States or Canada between fuel stops is Yakutat to Seward (or whittier, or Cordova) Alaska at roughly 320 NM

The furthest in Mexico that I’ve found is Turtle Bay to Cabo at something a bit over 430NM (by the charts as I’ve never made this trip)

But, for discussion sake...Our Bayliner holds 440 gallons of fuel. at 1.75NMPG that gives us a range of a bit over 600NM plus a 20% reserve at an 8 knot cruise speed. Way more than we will ever need.

The PO of our boat put in an extra tank, giving us 140 gallons to play with.

To estimate fuel burn I crunched the numbers for the whole of our first year which gave an overall fuel burn of 1.3gph...this includes warm ups, cool downs, crab trap fetching, and animal/whale photo ops. (We cruise at a set rpm and let wind & currents dictate speed over ground). For estimating I use 1.5gph.

This gives 429nm with a 33% reserve, or 518nm with a 20% reserve.

In our case it’s not how far it is between fuel stops, but how much meandering we can do. Last summer we hit all the mainland inlets in Fiordlands on the way home to Kitimat (but not Gardner Canal) after filling up in Shearwater without having to go to Hartley Bay.

In the future may convert the 50 gallon water tank into a fuel tank so we can stay out for even longer without having to “come in” to refuel. The price of water makers is holding that plan at bay...

38' Single 450 Cummins, 320gal in two tanks, call it 300 usable (I really can burn down to 5gal left in tank!!).

7.7kt at 1.9gph, 4.05nmpg, comes out to 1215nm range.

20kt at 11gph, 1.82nmpg, comes out to 545nm range.

Needless to say, I don't run with full tanks. Most I've had was like 250gal to do some Bahamas. Around SE USA, I keep 100-200gal on board to keep weight down.

Interesting that when planed out, boat does not seem to mind the weight in the aft tanks. Speed/rpm/boost numbers the same whether heavy with fuel or light. But at hull speed the heavy a$$ does have a slight penalty.

I carry 360 gallons and with a single FL 120 I average about 1 3/4 gal per hour at about 6.5/7 knots.
I'm not going to do the math, I know I can go farther than I need to on a load of fuel.

I've never had a chance to test the boat on a long trip to see what kind of fuel economy I get. I'm guesstimating that at hull speed, which is around 8.5kts, or below, I'm running at idle speed (550rpm) getting about 1.5kmpg. That puts my theoretical range at somewhere around 900 miles with a 20% reserve. The boat holds 700 gallons.


If I bump the speed up to around 11kts, I'm guesstimating my fuel burn at about .8-.9kmpg which would put my cruising range at around 630miles. The fuel economy goes down quite a bit because at that speed I'm pushing a pretty good size bow wave.

If I slow mine down to about 1800 rpm that gives me around 6 knots at 1GPH, or a bit little less if there is some wind and I can use the steady sails.

With 20% reserve on my 215 gallon tank that gives me a range of about 1200 miles.

I have an old 83' boat I bought looking for a high hull speed knowing it would give me economy at a decent speed. I also wanted the Detroit Diesels for the reliability on the ocean and their lack of electronic sensors and controls.
All tanks full I carry 2000 gallons. At 7 knots over 2800 nm. At normal 10 knot cruising somewhere above 2000 nm.

I run at 10 kts, burn 10 gph, carry 700 gallons. I could slow down but have no reason to. Usually I plan fuel stops based on convenience and time of day. No sense pulling up to a fuel dock at 2am.

I could probably double my range if I wanted to take twice as long but I don’t want to.

If we were to just take the fuel burn of the main into account it is right at 2.4 gph at 1600 rpm with a theoretical distance of 2,800 nautical miles. This is with no reserve, or genny and heater use taken into account.
With genny and heater use added in we are just under 3.0 gph rate.

The OA Mk 1 has 1000 gallons as standard. When I replaced the tanks I enlarged the aft tanks and now have 1240 gallons capacity. The objective was to be able to get from West Coast to Hawaii at a reasonable speed. The attached graph was using data from the seatrials when launched after refit, so about half load and clean bottom. Objective could be met!

At 1500rpm I use 4gph, make a bit under 8kn and have range (no reserve) of just under 2500nm.

These days I tend not to fill the aft tanks completely unless fuel is a good price or I'm about to take a long trip and use it. The boat trims a little stern down when chock full of fuel, and feels quite different when cruising. So I ought to add the 5' stern extension that a lot of the Mk1's have done to compensate. Additional cockpit space would be really nice too....

In theory 2 x 3500 litres (1850 gal) should give 3700 NM range @ a bit over 8 knots at 1250 rpm burning under 4 gph.
We usually do a bit over 7 knots @ 1150 rpm on passage so range should increase marginally.

I never go long distances. However I would have a 1,250 nm range at my normal 7 knot cruising speed with a 10% reserve. I do fill up the fuel tanks to avoid the hassle of filling up very often. We don’t have fuel in my little harbor. If we did, I would probably only fill to 1/2

With my 660 gallon capacity and normal cruise rate of 7 knots, I have a 2,000 miles range with a 15 % reserve. Did almost 2,000 miles last summer between fuel stops in the Great Lakes. Planning out fuel stops saved $ .50 to $1 per gallon. Well worth the effort. Interestingly, the fuel burn doesn't change between full and empty when going 7 knots.

Ted

Here is the range estimate from the builder of my Allweather. 112 gallon tank.


5 knots ~1 qt./hr. NMPG=~20 ~2000NM+
6 knots ~2 qts./hr. NMPG=~10 ~1000NM+
7 knots ~3-4 qts./hr. NMPG=~5 ~500NM+

320 gal, 6.8 knots, and 1.8 GPH give me me a theoretical range of well over 1000 miles. . We only use 20 gallons on a long cruising day so its pretty easy to find reasonably priced fuel along the way before even getting close to low. But I get anxious whenever the tanks get <100 gal remaining so that's the point where we include a fuel stop in our next few days travels.

O C Diver said:

With my 660 gallon capacity and normal cruise rate of 7 knots, I have a 2,000 miles range with a 15 % reserve. Did almost 2,000 miles last summer between fuel stops in the Great Lakes. Planning out fuel stops saved $ .50 to $1 per gallon. Well worth the effort. Interestingly, the fuel burn doesn't change between full and empty when going 7 knots.

Ted

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Thats great and that was my thought in this thread was to be able to cruise and pick when you buy fuel .

I really never travel to far but like the option of not buying from the over priced places

Don’t forget to factor in the generator burn.

It’s easy to miss but if you run long distances it can really impact your range.

k9medic said:

Don’t forget to factor in the generator burn.

It’s easy to miss but if you run long distances it can really impact your range.

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True I need to add that to my graph I have a fuel meter to add to it just have not done it yet

Enough to get to Hawaii at 8 knots +.

k9medic said:

Don’t forget to factor in the generator burn.

It’s easy to miss but if you run long distances it can really impact your range.

Click to expand...

On my boat, I wouldn’t need to run a genny while under way for long distances. The alternator and inverter handle my AC loads. Of course, I have propane cooking and diesel heat. No AirCon.

2450 gallons. At 7 knots, around 2.7 gph and 6,300 miles. At 6.5 knots, over 7,000 miles.

High Wire said:

320 gal, 6.8 knots, and 1.8 GPH give me me a theoretical range of well over 1000 miles. ...

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Same here except my speed is 6.3.

My tanks are small; only 2 X 120 litres @ 2nm/litre = about 480 nm. I have space for 4x 25 litre jerry carry to stretch that a bit.

Enough to cruise the east coast of Australia, but if I headed west past Ceduna I'd need over double the tankage to get across the Great Australian Bight. It is the longest unbroken coastal cliff face in the world, so its a long way between stops.

Delfin said:

2450 gallons. At 7 knots, around 2.7 gph and 6,300 miles. At 6.5 knots, over 7,000 miles.

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Nice

Delfin said:

2450 gallons. At 7 knots, around 2.7 gph and 6,300 miles. At 6.5 knots, over 7,000 miles.

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Ok, you win.

Ted

350 gals at 2 mpg including generator use. Easy math says 700 mile range, no reserve.

As measured during our trip from MD to GA

7000 mile range! That's awesome

Just got to Ketchikan. Last fuel was in Oak Harbor about three weeks ago.

I travelled 731.7nm in 97.94 engine hours and burned 194.3 gallons of diesel. That's an average speed of 7.47 knots at 1.98 gph, or 3.77 nmpg.

This includes furnace burn (not much, nice weather) and I never needed to turn on the generator (or plug into shore power...thanks solar!).

Theoretically I could do almost 1400nm on my 370 gallon capacity. Practically, I start looking for fuel after about 1000nm, or whenever I get out of Canada, whichever is first.