Cruisers: How Much Fuel?

[Dockhead]

Originally Posted by Boatguy30

so you were able to drive a 12.8m yacht at 4.7 knots on .75 litres per hour?

That seems extremely hard to believe. Double that consumption and it would be impressive and believable, but that simply seems impossible.

I believe it. Motor slow enough with a clean enough bottom and in calm enough conditions (or slight tailwind), and you need very, very little fuel to drive a displacement hull.

That's about .2 liters per mile, which I've seen on my 25 ton, 16.4 liter boat at 5 knots or so. Compared to "average" motoring at about one liter per mile at 7.5 or 8 knots.

[Jon Eisberg]

Originally Posted by Nicholson58

We have 380 gallons in 5 tanks.

I also carry jerry cans on deck - never leave with empty containers. On-deck stuff gets transferred to the main tanks ASAP.

380 gallons, and you still carry jerry cans on deck???

Hell, I've run 40' motor yachts that carry less fuel than that...

:-)

[downunder]

Originally Posted by zeehag

i seem to never carry enough and end up drifting in ocean for a coupla days until i am close enough to leapfrog into harbor. once i even had 3 gallons remaining iin tank. zihuatenejo i had less than an ounce, and that was in return line. ok.....so
figger out your gph and figger out how many hours at a speed over ground less than reality so you know that you will mebbe have almost enough to make port without drifting, and then add one more jerry jug to the mix so you are ok. mebbe--it also depends on uphill or down hill sailing .....

Good demonstration that many do not carry enough fuel. Always best to have addittional tankage built in rather than carrying on deck in jerrycans. No doubt there are cruising areas particually in the doldrums where extra fuel is always useful and preferable to chasing dodgy fuel in drums. Then again many vessels are not designed for cruising areas where fuel is not readily available.

Skipper needs to know the fuel burn per hour as well as distance to travel as speed over ground varies.

[svmariane]

It's all a matter of perspective, no?

Fully loaded, we've 250 US gallons in one tank beneath the sole, augmented by four of those 5 USG / 20 litre jugs up on deck, normally tied to the quarter hard-rails. Because stuff happens.

Coming into Haʻapai, Tonga, out of Niue...
Reefs, Isles, tricky winds....
Navigator's Nightmare.....
Tried to motor in...
Fuel pump on main motor gave out....
Rigged aux 12 vdc fuel pump...
Then the aux fuel pump clogged up....
Do we sail & drift out of the area, then heave to and try to sort things?...
What to do.....

Photo shows my answer. Siphon feed, baby.

And the smile on my wife's face when we dropped anchor told me all I need to know about innovation, taking precautions (spare stuff) and having back-up plans to the other back-up plans....


{Sailor's Confession: Should have rigged the 12 vdc pump AFTER the fuel filter, not closest to the tank. I was in a hurry - didn't think it through - and that's never a good thing. Live & learn.... }

[StuM]

Originally Posted by Terra Nova

Does anyone actually do this? Over-rev their engine just because the wind is blowing? No. Except when idling, boat engines are normally operated at "cruise" rpm. This does not change, like driving a car in traffic, shifting through the gears, constantly varying rpm to maintain position in traffic, and as required by stop lights.

Not me. I know what my fuel curve looks like and how much that extra couple of hundred revs will cost me in higher fuel burn. I look at the new VMG I'm am achieving and calculate how many hours it will now take to the destination. If I don't like the answer I will likely reduce revs (and VMG) to get greater range.

As you say, it takes completely different considerations compared to driving a car.

[Dockhead]

Originally Posted by StuM

Not me. I know what my fuel curve looks like and how much that extra couple of hundred revs will cost me in higher fuel burn. I look at the new VMG I'm am achieving and calculate how many hours it will now take to the destination. If I don't like the answer I will likely reduce revs (and VMG) to get greater range.

As you say, it takes completely different considerations compared to driving a car.

Yes, but sometimes you just need to go upwind and sometimes need the motor for some or all of the power required. The power required goes up exponentially when you try to overcome head seas, and you can't just slow down and use the same amount of fuel. It's always better to sail when you need lots of power, but you can't always do that.

For example, getting out of Borkum through the riffgat against a F7 and horrible chop, dead upwind and no room to tack. About 10 miles of this torture. 3000 RPM got me about 2 knots SOG so those 10 miles cost me at least 80 liters of fuel despite having been able to motorsail a little from about half way out. It would not have been possible at lower RPM. Of course given a choice you would wait for better conditions, but the forecast was for the F7 to turn into an F8 and blow for days, so I had to bug out of there.


Thread drift, but this is also about the importance of having enough engine power, for cruisers like me who sail in all weather and long distances. In normal conditions, I rarely use more than 2000 RPM, probably mostly 20 horsepower or less out of my engine's 100 hp max. But man, when you need the power, you REALLY need it. I really like the Hallberg Rassey 64 with the 300 (!) horsepower six cylinder Volvo, and beam hardly wider than my present boat. Bashing through Borkum Riff would have been an entirely different experience in that boat.

[Ericson38]

Originally Posted by Dockhead

For example, getting out of Borkum through the riffgat against a F7 and horrible chop, dead upwind and no room to tack. About 10 miles of this torture. 3000 RPM got me about 2 knots SOG so those 10 miles cost me at least 80 liters of fuel despite having been able to motorsail a little from about half way out. It would not have been possible at lower RPM. Of course given a choice you would wait for better conditions, but the forecast was for the F7 to turn into an F8 and blow for days, so I had to bug out of there.


.

So at 100 hp (more or less), 10 nm at 2 knots, or ~ 5 hours, and you consumed ~ 80 liters of fuel (21 gallons), which comes to about 4 gallons per hour. That is like 25 hp per gallon per hour, a little better than the observed average, maybe because a Turbo (Yanmar ?) ?

Just asking as our new to us Taswell 49 with 125 gallon fuel tank has a 77 hp Turbo Yanmar (4JH2-HTE). BTW, 4JH4 means 4 valve head, 4HJ3 means 3 valve head.

Interesting that you spend a lot of cruising time at 2000 rpm or thereabouts, versus the recommended 3000 plus range for Yanmar (if that is what you have). I also like not running her at 80% of rated for the same reasons you cite, basically the exponential growth in hull resistance through the water once past 60-70% of hull speed.

[exMaggieDrum]

The new boat only has 45 gallons of fuel capacity. We intend to cross oceans at some point so I am very concerned that this is enough. But our previous boat was anything but a nimble, go to weather boat, and we motored constantly, using most of our 225 gallons of fuel a couple of times. We would motor for days on end. We would have rather sailed but didn't. To this day, I am slightly red-faced to admit this. But it gave great peace of mind, especially when bashing to windward for a thousand miles in headwinds and rough seas (twice).

So I am trying to see if I can add an additional fuel tank down below. Anything would help but I would love to more than double what I have. It would be great if I never touch it but in the Pacific Northwest you have to motor far more than even the most diehard sailor would like, so would have a chance to keep it fresh. I don't like fuel jugs on deck either but it I do like the idea of having some fresh fuel if I miscalculated my usage/fillage, or developed a leak in the main tank, or it got dirty/water etc. For emergency purposes.

The new boat is a much better sailor and others with the same tankage have not had to use much fuel. But time will tell what my personal experience is. But I never want to run out - never. Same for water. So I will be conservative and even close to home port I will at least carry a 5 gallon jug somewhere, if not more.

I did some research on bladder tanks. Don't even consider them for a sailboat. They are not suitable for below deck. The manufacturers that I visited specifically forbid it. And the lashings required for putting one on deck would redefine ugly.

[Dockhead]

Originally Posted by Ericson38

So at 100 hp (more or less), 10 nm at 2 knots, or ~ 5 hours, and you consumed ~ 80 liters of fuel (21 gallons), which comes to about 4 gallons per hour. That is like 25 hp per gallon per hour, a little better than the observed average, maybe because a Turbo (Yanmar ?) ?

Just asking as our new to us Taswell 49 with 125 gallon fuel tank has a 77 hp Turbo Yanmar (4JH2-HTE). BTW, 4JH4 means 4 valve head, 4HJ3 means 3 valve head.

Interesting that you spend a lot of cruising time at 2000 rpm or thereabouts, versus the recommended 3000 plus range for Yanmar (if that is what you have). I also like not running her at 80% of rated for the same reasons you cite, basically the exponential growth in hull resistance through the water once past 60-70% of hull speed.

Opinions vary, but I think that the idea that you must use 80% of your engines power is nonsense. I think almost any engine speed is ok as long as you have some load on. I follow the Yanmar manual rather than people's opinions. The manual says that if you run at low speeds for long periods of time, "blow it out" once and a while at high load and RPM. I do this.

My engine even has an optional "trolling lever", for operation at under 1000 RPM for trolling. Yanmar would never offer such a thing, if it were harmful to operate the engine at low speeds.

The important thing is to have some load on, and with a variable pitch prop (I have an Autoprop), this is not a problem.

I like to sail fast and motor slow (or not at all, if possible). In a dead calm I might motor at 6 knots or 6.5 at 1600 to 1800 RPM. I am using less than 2 liters per hour at this speed, so say .33 liters per mile.

This goes up very sharply if I run the motor up to 2300 (still a relaxed speed for this 3900 RPM engine). Then it's maybe 5 or 6 liters per hour or double or triple the fuel consumption per mile. For another knot or at most knot and a half maybe of speed. A compromise is 2000 RPM at around 7 knots in calm water with a clean bottom, if I need a bit more speed.

You have no choice, however, if you are punching through head seas or have wind against you. Then I might well use 2500, 2800, even 3000 RPM, at the cost of exponentially increased fuel consumption per mile. But sometimes you gotta do, what you gotta do

[Jon Eisberg]

Originally Posted by svmariane

It's all a matter of perspective, no?

Fully loaded, we've 250 US gallons in one tank beneath the sole, augmented by four of those 5 USG / 20 litre jugs up on deck, normally tied to the quarter hard-rails. Because stuff happens.

Coming into Haʻapai, Tonga, out of Niue...
Reefs, Isles, tricky winds....
Navigator's Nightmare.....
Tried to motor in...
Fuel pump on main motor gave out....
Rigged aux 12 vdc fuel pump...
Then the aux fuel pump clogged up....
Do we sail & drift out of the area, then heave to and try to sort things?...
What to do.....

Photo shows my answer. Siphon feed, baby.

And the smile on my wife's face when we dropped anchor told me all I need to know about innovation, taking precautions (spare stuff) and having back-up plans to the other back-up plans....


{Sailor's Confession: Should have rigged the 12 vdc pump AFTER the fuel filter, not closest to the tank. I was in a hurry - didn't think it through - and that's never a good thing. Live & learn.... }

Perhaps I'm missing something from your account, but that story reads more like an argument for having an inline 12V fuel pump permanently plumbed into your system, than one for the carrying of additional fuel in jugs on deck ;-)

And, if your jury-rigged 12V pump itself got clogged, you must have had some seriously nasty **** in your main tank, it generally takes some serious doing to clog a pump in such a short time, even without the benefit of a filter...

I'm surprised the practice of permanently installing a 12V pump isn't more widely adopted, but I rarely see it on the boats I run. My own little Perkins M-30 doesn't have an electric fuel pump, but I believe the utility of having an inline pump installed, ready to go at the flick of a switch, cannot be overstated. Very handy for topping up a Racor after a filter change, or bleeding the engine itself, not to mention the ability to 'encourage' many engines to keep running when sucking some air, or dealing with some undetermined restriction of the flow of fuel... And, if I had a Westerbeke, or any other engine dependent upon an electric fuel lift pump to keep running, there is no way I'd want to be without an backup 12V pump inline, and ready to go at the first indication of a problem...

Another fuel storage issue I feel needs to be better addressed today, is that for the provisions for carrying gasoline. With so many cruisers now full embracing the use of both Honda portable generators, and relatively large outboard engines for their SUV dinghies, seems it's high time for boatbuilders to be allocating dedicated belowdecks gas storage tanks, as well... Perhaps some builders of larger yachts are doing so, but none immediately come to mind... In he meantime, seems many folks are out there using some pretty shaky arrangements for carrying and storing one of the most dangerous fuels of all... When I got aboard the V-42 I was to bring back from Antigua a month ago, I discovered that the owner had stowed his almost-full gas tank for his tender in the bottom of one of the cockpit sail lockers!

Yikes...

[downunder]

Originally Posted by Jon Eisberg

Perhaps I'm missing something from your account, but that story reads more like an argument for having an inline 12V fuel pump permanently plumbed into your system, than one for the carrying of additional fuel in jugs on deck ;-)

And, if your jury-rigged 12V pump itself got clogged, you must have had some seriously nasty **** in your main tank, it generally takes some serious doing to clog a pump in such a short time, even without the benefit of a filter...

I'm surprised the practice of permanently installing a 12V pump isn't more widely adopted, but I rarely see it on the boats I run. My own little Perkins M-30 doesn't have an electric fuel pump, but I believe the utility of having an inline pump installed, ready to go at the flick of a switch, cannot be overstated. Very handy for topping up a Racor after a filter change, or bleeding the engine itself, not to mention the ability to 'encourage' many engines to keep running when sucking some air, or dealing with some undetermined restriction of the flow of fuel... And, if I had a Westerbeke, or any other engine dependent upon an electric fuel lift pump to keep running, there is no way I'd want to be without an backup 12V pump inline, and ready to go at the first indication of a problem...

Another fuel storage issue I feel needs to be better addressed today, is that for the provisions for carrying gasoline. With so many cruisers now full embracing the use of both Honda portable generators, and relatively large outboard engines for their SUV dinghies, seems it's high time for boatbuilders to be allocating dedicated belowdecks gas storage tanks, as well... Perhaps some builders of larger yachts are doing so, but none immediately come to mind... In he meantime, seems many folks are out there using some pretty shaky arrangements for carrying and storing one of the most dangerous fuels of all... When I got aboard the V-42 I was to bring back from Antigua a month ago, I discovered that the owner had stowed his almost-full gas tank for his tender in the bottom of one of the cockpit sail lockers!

Yikes...

+1

[svmariane]

Originally Posted by Jon Eisberg

Perhaps I'm missing something from your account, but that story reads more like an argument for having an inline 12V fuel pump permanently plumbed into your system, than one for the carrying of additional fuel in jugs on deck ;-)

And, if your jury-rigged 12V pump itself got clogged, you must have had some seriously nasty **** in your main tank, it generally takes some serious doing to clog a pump in such a short time, even without the benefit of a filter...

I'm surprised the practice of permanently installing a 12V pump isn't more widely adopted, but I rarely see it on the boats I run. My own little Perkins M-30 doesn't have an electric fuel pump, but I believe the utility of having an inline pump installed, ready to go at the flick of a switch, cannot be overstated. Very handy for topping up a Racor after a filter change, or bleeding the engine itself, not to mention the ability to 'encourage' many engines to keep running when sucking some air, or dealing with some undetermined restriction of the flow of fuel... And, if I had a Westerbeke, or any other engine dependent upon an electric fuel lift pump to keep running, there is no way I'd want to be without an backup 12V pump inline, and ready to go at the first indication of a problem...

Yikes...

All good points.

Yeah, our fuel was crappy. 250 Gal below decks but we mostly sail, even on/off the anchor. Fuel got old, with lack of proper attention to the prob. All my fault. With our fuel burn, some of that diesel was probably in the tank for more than five years. Situation now rectified.

12 vdc pump was an after thought, purchased in Mexico days before departure. Now have two: one permanently installed - AFTER the first filter - and the second in the spares locker. T'was something I learned about from another sailor whilst hangin' round the pub.

When I win the Lotto I'm a gonna buy me one of them thar dual-filter systems with switching valves.

I admit prior naivety to some potential fuel issues before the s**t hit the fan. I know {a bit} better now. And next time, of course, something ELSE will probably bite my backside.

Ain't cruising fun?

[Eleuthera 2014]

Originally Posted by Dockhead

You need enough fuel not to worry about it, to put it simply. How much that is is not subject to a simple calculation. For one thing, liters per mile varies enormously depending on conditions. Downwind or in a dead calm motoring slowly or motor-sailing, we consume from nearly zero to a maybe .5 liters per mile. That's at 1200 -- 1600 rpm. Faster motoring (2300 rpm) will use about a liter per mile. Fighting headwinds or currents, this can go up manyfold -- up to perhaps 5 or 6 liters per mile or even more. Dirty bottom or clean also makes an enormous different in fuel consumption.

We have 678 liters on board, which could be enough for a couple thousand miles or only enough for a couple hundred -- depending on the conditions.

We also heat and generate electrical power with diesel fuel, so that also needs to be taken into account. And making water, if you have a watermaker.

I'm about 900 miles from Helgoland, where we last filled the tanks. We've got about half a tank left, so we've used maybe 300 to 350 liters. We've done some motoring (including 65 miles of mandatory motoring through the Kiel Canal), but we've had no headwinds, so almost no motoring over 2000 RPM. We've made a lot of electrical power and done some heating. YMMV, literally, and to say the least. This amount of fuel would be ok for a tradewinds Transat, since there will be less than usual motoring, but I wouldn't actually want any less. And I would certainly have some jerry cans in the lazarette or behind the transom platform. At least 100 liters, I would say.

Equipment run on diesel fuel: 100hp Yanmar main engine, 6.5kW Kohler generator, 10kW Eberspaecher central heating system.


One thing which I would really hate would be to have to conserve electrical power because I don't have enough fuel to generate. This is misery. I would never want to be on any boat where you don't just fire up the generator or main engine and generate all the power you need.

Dockhead and I share the realities/opinions regarding fuel quantity.

We have 600 liters and if pooling at 1200-1400 rpm, we can motor for 1000nm +. (In ideal conditions) However, the genset uses about 2 l/hr but is only used when making water. But this seldom happens as our H2O is 1000 liters.

To ensure clean exhaust elbow, we run the diesel at 2800 rpm for at least 1 hour every 20.

No ugly jerry cans for us...

[lifeofreilly57]

Originally Posted by svmariane

It's all a matter of perspective, no?

Fully loaded, we've 250 US gallons in one tank beneath the sole, augmented by four of those 5 USG / 20 litre jugs up on deck, normally tied to the quarter hard-rails. Because stuff happens.

Coming into Haʻapai, Tonga, out of Niue...
Reefs, Isles, tricky winds....
Navigator's Nightmare.....
Tried to motor in...
Fuel pump on main motor gave out....
Rigged aux 12 vdc fuel pump...
Then the aux fuel pump clogged up....
Do we sail & drift out of the area, then heave to and try to sort things?...
What to do.....

Photo shows my answer. Siphon feed, baby.

And the smile on my wife's face when we dropped anchor told me all I need to know about innovation, taking precautions (spare stuff) and having back-up plans to the other back-up plans....


{Sailor's Confession: Should have rigged the 12 vdc pump AFTER the fuel filter, not closest to the tank. I was in a hurry - didn't think it through - and that's never a good thing. Live & learn.... }

Like your attitude.
If your going to out of the way places you better have more than one plan and the knowledge to innovate.
Theres always another way.....

[Jon Eisberg]

Originally Posted by Eleuthera 2014

No ugly jerry cans for us...

Well, if you were among the herd of East Coast snowbirds, you would definitely be part of a very small minority :-)

Just did a 'wrong way' trip from Annapolis to Lauderdale. I was outside most of the way south of Morehead City, but running against the grain of the last of the fleet returning from their winter spent south on the Chesapeake, and the 200 miles of the ICW behind Hatteras, affording the opportunity to cross paths with a significant number of those cruisers...

Wish I had kept a record to determine a rough percentage, but it seems pretty much everyone is carrying additional fuel on deck... At least 75%, would be my guess. Of course, this if for a trip motoring up the freakin' Ditch... I can only wonder, would these same folks strap on additional gas cans onto the rear bumper or roof racks on their SUVs for a trip down I-95 to Disney World?

:-)

Certainly not like I haven't been seeing this for years, but it never ceases to amaze, how comparatively few of these mobile fuel barges were actually sailing :-) I left Annapolis the day after Memorial Day, and there was a sustained and pretty brisk southerly flow for the next few days. A PITA for me, but ideal for those heading up the Bay, or across Currituck and Albemarle Sounds... OK, I know it's none of my concern how others choose to run their boats, but I'll always remain an 'interested observer' :-) And, it can become a bit of an annoyance after awhile, punching into 25-30 knots across the mouth of the Potomac on a 34' Beneteau without a dodger, while watching a steady procession of boats with full cockpit enclosures motoring downwind without so much as a scrap of headsail unfurled...

No wonder the builder's standard tankage never seems to be enough...

:-)