Willard 36 sedan fuel consumption

In January I changed the oil and got fuel in the same weekend while diesel was 1.89 dollars a gallon and wrote down 1700 hrs and 300 gallons,today i hit 1801 hrs dipped my tanks and got 220 gallons,the dipstick onboard is quite accurate as i had checked it while pumping fuel,so im very confident in the calculations,that puts me at 1.25 gallons per hr over 101 hrs running the Broadbill at 1500@7+ knts,in favorable conditions,she holds 500 gallons,so by my calculations thats a true long range cruiser,if i pulled her back to 5 knots im guessing 4000 mile range or so,does that sound correct

Lostsailor13 said:

In January I changed the oil and got fuel in the same weekend while diesel was 1.89 dollars a gallon and wrote down 1700 hrs and 300 gallons,today i hit 1801 hrs dipped my tanks and got 220 gallons,the dipstick onboard is quite accurate as i had checked it while pumping fuel,so im very confident in the calculations,that puts me at 1.25 gallons per hr over 101 hrs running the Broadbill at 1500@7+ knts,in favorable conditions,she holds 500 gallons,so by my calculations thats a true long range cruiser,if i pulled her back to 5 knots im guessing 4000 mile range or so,does that sound correct

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At 5 knots you're figuring 8 nmpg? I.e., 4,000 miles divided by 500 gals. Don't forget you want a 20% fuel reserve! Which means you have 400 safely usable gallons. Which equals 3,200 miles before refueling is considered.

Also... your boat's nmpg is calced from/as nmog. There could be tidal currents that either reduce or increase that speed over ground. Winds and sea conditions can also alter nmog per hour

Be careful!!

The Willard being a full displacement hull type certainly will be efficient, but I can't believe 8 Nmpg even at 5 kts.

David

If 1.25 gal / hr at 7 kts is accurate, that's 5.6 nmpg. So close to 8 nmpg at 5 kts might be possible. It's not unheard of for similar size sailboats when motoring a couple kts below hull speed, so if the W36 hull shape and drivetrain is equally efficient as a package, I could see it.

In 1987, a Willard 36 pilothouse went from Southern California to Hawaii - the favorable direction. The PH is a Blaine Seely adaptation featured in Voyaging Under Power and carries a small sail plan so may have had a bit of push, but she also carries 300g of diesel (vs 500 for the sedans). The owner carried fuel in a bladder in the cockpit. Boat was equipped with a Perkins 4.236 75hp diesel and burned 335 gallons over the 15-day run, so averaged around 6kts covering at least 2200 nms. That is around 0.9 gph, or in the neighborhood of 6-3/4 nmpg.

The first W36 hull was launched in 1961 with 38 more hulls to follow through 1970 (mine being the last W36). I am pretty sure it was the first long-distance production trawler in the world - preceding PAE's N46 by 20+ years. W36's have made many, many remarkable voyages in the days long before modern electronics. 25-years ago, I salvaged a stack of mimeographed newsletters off Rattler, W36 Hull #1. The owner of Linco, Hull #4, a lawyer from Portland OR, would gather insights from various owners and publish the newsletter a couple times a year - an early version of TrawlerForum if you will. In the 1960's owners took their W36s as far away as Galapagos Islands and the Panama Canal. At the time, few boats had even VHF radios - I cannot imagine trekking south along Central/South America with zero electronics beyond some form of knotmeter and depthsounder, and no communications.

Despite the above, I do not consider the W36 to be suitable for transoceanic passages without significant modifications to quickly shed green water. Nonetheless, these are remarkable little boats with proven capabilities.

I run my W36 w/4.236 at around 1700 RPM which averages around 6.8 kts in open-water. I have never been able to confidently/accurately measure consumption, but would guess it's in the neighborhood of around 1.2 gph. 8-nmpg might be a stretch even at 5 kts, but not a wild stretch, if at all.

Peter
(Co-Moderator since 1999, Willard Boat Owners Group)

Meaningless but fairly interesting!

If we brought our Tolly twin screw gasser down to about 4 knots running on one engine at a time [BW Velvet Drive trany allow freewheel prop spin]: I'm confident we could maintain 1.25 +/- gph which equals 3.5 +/- nmpg. God help us if running into tidal current... we'd be close to standstill. Sooo... with 200 gal gas aboard and 160 gals before fill-up is recommended... that = only 640 mile range at 4 knots while still maintaining fuel to spare. Could always put 200 gal more fuel aboard in temp bladders. That still limits our Tolly to 1280 nautical mile range... while maintaining fuel reserve safety.

You might be asking... why did Art even bother to compose this "not much use" post??? Similar to the question I ask about other posts in this thread.

2 reasons:

#1. To imply it is crazy that are we even discussing any of our relatively small pleasure boats as passage makers. They simply do not have the size and scope to be such. I recommend using them for their design intended purpose - i.e. "Pleasure"

#2. I'm bored this morning waiting for a business email reply!

Happy Cruise-Range Daze! - Art

"Hull Speed" is an estimate number which varies from boat to boat ,
Sq RT of LWL times 1.34 is an informed guess.

It is possible to slow too much and burn more fuel from skin friction , instead of from wave making.

The usual best estimate guess for economy is the SQ RT of the LWL ,
tho times .9 to times 1.1 works .

FF said:

"Hull Speed" is an estimate number which varies from boat to boat ,
Sq RT of LWL times 1.34 is an informed guess.

It is possible to slow too much and burn more fuel from skin friction , instead of from wave making.

The usual best estimate guess for economy is the SQ RT of the LWL ,
tho times .9 to times 1.1 works .

Click to expand...

How easily too slow happens depends on the efficiency curve of the engine(s) as well. Some setups keep getting more efficient all the way down to idle, others don't gain much below a point. And then there's the efficiency vs going annoyingly slow tradeoff...

FF said:

"Hull Speed" is an estimate number which varies from boat to boat ,
Sq RT of LWL times 1.34 is an informed guess.

It is possible to slow too much and burn more fuel from skin friction , instead of from wave making.

The usual best estimate guess for economy is the SQ RT of the LWL ,
tho times .9 to times 1.1 works .

Click to expand...

Our Tolly's 32' WLW sq-rt is 5.66 / X 1.34 = 7.58 knots / X 1.1 = 6.23 knots

Have found... Most fuel efficient cruise with twins both running is 6.5 to 7 knots.

Which leads me to believe that 1.2 is our Tolly's magic # of calculating "hull speed" for attaining least fuel cost and still make headway in a timely fashion. Of course... going against a 3 knot current means ya might as well anchor till tide pattern reverses! Or, of course; can always up the throttle, plane along at 16 to 17 knots - and - get to destination in due time anyway! And, if you really need to go-somewhat-fast [while not beating engines to a pulp] 20 knots continued speed is available... as 22 to 23 is WOT.

Then there's super economy slow-speed: 4 to 4.5 knots with only one engine running. I make damn sure boat's traveling in same direction with the current at this minimal mog speed.

3 +/- nmpg at super economy speed / 2 +/- nmpg at hull speed / 1 +/- nmpg at 17 planing speed

Captain's cruise speed choices are several in a planing hull that has ample power.

Lostsailor13 said:

In January I changed the oil and got fuel in the same weekend while diesel was 1.89 dollars a gallon and wrote down 1700 hrs and 300 gallons,today i hit 1801 hrs dipped my tanks and got 220 gallons,the dipstick onboard is quite accurate as i had checked it while pumping fuel,so im very confident in the calculations,that puts me at 1.25 gallons per hr over 101 hrs running the Broadbill at 1500@7+ knts,in favorable conditions,she holds 500 gallons,so by my calculations thats a true long range cruiser,if i pulled her back to 5 knots im guessing 4000 mile range or so,does that sound correct

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But it dosn’t account for hours of running for various reasons. Startup, no wake zones ect ect.
Most think it’s fly stuff and dosn’t count.
But most all of your light running moments are almost immediately forgotten.
I’d guess your fuel burn is more like 1.5 gph. But at any rate your gph is most affected by what you do w the throttle. My fuel burn as calculated much the same as yours came to almost exactly 1gph but I probably run my engine a bit harder. My W30 runs at 2300rpm .. not overpropped.
I think if I pulled Willy back to 5 knots we could run Seattle to Juneau on one tank .. 100 gallons.
My favorite Willard hull is by far the W36.
If Willard had made a W30 w the 36 hull it probably would be a W28. The W36 has a huge volume per foot of displacement.

Nomad Willy said:

But it dosn’t account for hours of running for various reasons. Startup, no wake zones ect ect.
Most think it’s fly stuff and dosn’t count.
But most all of your light running moments are almost immediately forgotten.

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That's a very good point. Most people don't realize just how much time you spend running below cruise speed unless you're making a long, continuous passage.

rslifkin said:

That's a very good point. Most people don't realize just how much time you spend running below cruise speed unless you're making a long, continuous passage.

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Amen to that. When I was delivering, I stopped asking people what their fuel-burn was. First, I had a better idea than they did. Second, when they had an idea, it was overly optimistic. By a LOT.

Good article on hull-form and various coefficients by Chuck Neville (NA) from an old Passagemaker Magazine. I wish I had some way to estimate the Pc (Prismatic Coefficient) for my W36, but I suspect its in the mid/upper 50s. As Nomad Willy states, the W36 hull is indeed special - Bill Garden got it right.

That said, I am constantly disappointed by the largish engines some displacement boats have. My 75hp Perkins is perfect. A 135hp Perkins 6.354 was offered as an option that many went with which was, in my opinion, simply too big. Like the OP, a few had larger DDs that, while decent engines, were a bit big for the boat.

https://www.passagemaker.com/web-extras/magic-hull-shape


Peter

Thanks Peter .. that’s the real deal.
And rslifkin Thanks to you as I thought I was going to get flying tomatoes.
And the overpropping can be a small benefit depending on throttle induced load.

The Passagemaker article is great. They mention doing a lot of comparing. I have. Mostly re a ratio of hp per ton. I remember I even calculated an Alaska State ferry. It’s interesting and obvious why it’s so that the bigger boats get the lower the installed power. Really bigger boats like ferries and tugs usually have the amount of power actually needed. The call being made by a NA. And with a yacht the boat owner or boat owner to be probably and frequently says “Are you sure that’s all the power this boat needs”? They likely tend to think that their car is 1/4 the size and has four times as much power.

FF wrote;
“It is possible to slow too much and burn more fuel from skin friction , instead of from wave making.”

I’ve thought about that and always dismissed it on a need to know basis.
It’s clearly well to way below most people’s cruising speed.
That may be where overpropping could shine. But who wants to go cruising at idle?

This w36 hull has amazed on a number of platforms,and the compliments are daily,although it is definitely overpowered this 453n is starting to grow on me,between the availability of parts and at very good prices,the simplicity of the fuel system,very easy to work,and then the biggest one the reliability of a well cared for Detroit,my boss has a front end loader with the 353n with 50,000 original hrs that engine would have been real sweet in this hull,and on anther note ive begun my Dickinson heater install started with building California closet in foc'sle which heater will mount to and have almost all my parts ordered so in the next week or so will be starting a new Dickinson heater install thread

Hulls and engines

Thank you, Peter, for attaching the Neville article on Hull Shape from PassageMaker. I had forgotten that one, or was too wrapped up in purchasing my boat (Camano 31) at the second publishing date, and started dating the Admiral at the initial publishing date. It clarifies so much. It also matches well with a class I took at Trawlerfest in 2016, Steve Zimmerman's "How to buy a boat", which connected planned boating activities, numbers of passengers, etc., to sizes and types of boats. I was already a fan of Camanos when I took that class, and it didn't take much creativity to connect my biases to the information and worksheets that Steve provided. (Surely, I'm not the only one who rationalizes boat dreams to sound like real expertise, am I?) So, after a New England to NC delivery, I'm happily cruising Albemarle and Pamlico Sounds and the wide rivers that feed what is the second largest estuary on the East Coast, ample colonial small towns and undeveloped shorelines to visit, while planning more extensive trips for the future - perhaps Philadelphia and Jacksonville FL as brackets on those plans.

One of the additional thoughts for this link is another one of Steve's articles regarding the necessity of operating at adequate levels of engine "effort" to keep the engine healthy....a mature and more moderate version of what some of us as teenagers felt was frequently necessary to maintain our parent's boulevard cruisers of the 1960s, "blowing out the carbon". Even my Volvo's manual references higher RPM on a given frequency for overall engine health. Those of us with trawlers with additional "beat the storm" horsepower can be overly comfortable around fuel sipping hull speed and find exhaust components partially clogged with carbon sludge, as I did in my first year of operation. So, engines sized to hull speed and a little more probably don't face that risk, and semi displacement hull owners with plaining capability need to include "percent of maximum effort" advice from Steve - using higher GPH/WOT-GPH ratios on a planned basis to keep the engine healthy. He notes the subject under the subtitle, "Perils of an Easy Life" in this article:
https://www.passagemaker.com/technical/how-long-will-my-engine-last

Thanks again, Peter, and other TF contributors for an enlightening discussion.

...a mature and more moderate version of what some of us as teenagers felt was frequently necessary to maintain our parent's boulevard cruisers of the 1960s, "blowing out the carbon".

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“Drive it like you stole it...”

mvweebles said:

As Nomad Willy states, the W36 hull is indeed special - Bill Garden got it right.

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Garden specified the Gray Marine conversion of the Continental HD277 4 cyl Diesel for the W36. It was rated 50 hp @ 2000 rpm continuous, or 60 hp @ 2200 rpm intermittent. Several of the older boats still have that engine including Solitude and Island Seeker. I had it in hull #6, and consider it the perfect match to the hull. As I recall made just over 7 knots at 1700 rpm.

Continental quit building it in about 1963, which I assume triggered the change to Perkins.

I had the head off due to a gasket leak with the hour meter reading 8500 +/-, and the cylinders were like new, still had the hone hatch marks. It had a big two shaft balancer, and a flywheel that must have weighed 100 pounds, ran smooth as silk. Bill Garden got the engine spec right too!

Bill

"How easily too slow happens depends on the efficiency curve of the engine(s) as well. Some setups keep getting more efficient all the way down to idle, others don't gain much below a point. And then there's the efficiency vs going annoyingly slow tradeoff.."

TRUE, But sadly the engine mfg or converters are very reluctant to publish the BMEP graph for their products in the smaller size. Under 500hp or so.

BMEP can be had for large engines , it looks like a bulls eye, the center covering the best fuel/hp area and the rings outside show the info for less efficient loads/fuel burn.

The smaller engines come with a "prop graph" which sometimes is accurate for a few hulls , but useless to setting a boat up for normal operation, which may include fast running as well as long range cruising.

The prop demand curve will still give some idea of how efficiency drops off if they publish both hp demand and gph burn. Even if the graph doesn't match up to the hull you're using, it'll still tell you if the hp-hr per gallon drops off significantly at some point in the range.