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Old 17-07-2017, 14:45   #16
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Re: Fuel consumption - real world numbers

Can't read too much about saving on fuel!
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Old 17-07-2017, 14:55   #17
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Re: Fuel consumption - real world numbers

I have owned several inboards and outboards, both gas and diesel, sailboats and inflatable dinghies.

Across the board, I have found that reducing power to about 70% reduces speed only a little but decreases noise and stress by a large margin. And fuel economy doubles, at least.

WOT = wide open wallet.

On longer sailboat passages, reducing rpm to go (for example) 4 knots instead of 5 knots would effectively DOUBLE my range (in miles). Its shocking. The only problem is...its so hard to go slow, when you could be going fast.
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Old 17-07-2017, 15:15   #18
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Re: Fuel consumption - real world numbers

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Originally Posted by JohnEasley View Post
I did a little number crunching this morning on fuel consumption and costs and was so stunned by the results that I decided to share.

We have a 42' 1986 Chris Craft aft cabin. She weighs in at 36,000 lbs and has been repowered with 330 hp Cummins 6BTA diesels.

In May, we took her from near Tampa, FL to the Florida Keys for a two week trip. During that trip, there were stretches near bridges, marinas, and no-wake zones where we were at minimum wake speeds but most of the time we ran her at cruising speed of 2300 rpm, which works out to about 19 mph on plane. The trip was 501.6 miles long. Some of it was Intercoastal waterway and some was open Gulf waters. We used 693 gallons of fuel for a cost of 1925.89. This worked out to 14.6 gallons per hour or about .7 miles per gallon. Overall, we were pretty pleased.

Then we got home and started looking at the log book entries. By the time we motored in and out of anchorages or marinas, passed through no wake zones, etc, we were averaging about 9.9 mph for the whole trip. Really???

After discussing with a couple of friends, we decided to do a test. We filled her up, did 86 miles in two day trips, and then filled her up again. During the day trips, we ran the engines at "cruising" speed of 2300 rpm for about five minutes to blow out the turbos but otherwise kept the speed at about 1400 rpm, which yielded 10 mph with some trim tabs engaged. When we refilled, we took in 43 gallons. This worked out to 4.9 gallons per hour or 1.58 mpg! The two day cruises were less noisy and almost... serene. We still got to our destinations without a significant delay and still had a great time.

So, we took the slower burn rate and recalculated the recent Keys trip. If we had used the same approach as the two test trips, we would have used well under half the fuel and would have saved nearly $1100!!! We were pretty shocked.

Your mileage may vary.

Still Learning John
700 gallons!!! In my Jeanneau 37 yacht I could cruise for 5 seasons (three Month holidays) a year. We traveled about 5/600 miles a year
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Old 17-07-2017, 15:48   #19
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Re: Fuel consumption - real world numbers

I recently read an article regarding motor catamarans vs sailing catamarans in the med. I recall that when when the cost of sails, distance covered, speed over a set time were factored, the motor catamaran was cheaper to operate.

Go figure..
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Old 17-07-2017, 16:03   #20
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Re: Fuel consumption - real world numbers

Still working on finding my 4-cylinder, 30hp westerbeke's fuel consumption/speed "sweet spot", but currently 2000 rpms, at 0.5 U.S. gal/hr, drives her 16000 lbs from 4.5-6.5 knots, dependent on sea conditions, when not using sails. Granted it takes me 9-10 hrs to go from Guilford, Ct to Block Is (approx. 50 nm) while my friend does it in 2 - 2.5 hrs w/ 2 gasoline powered V8's in his 32 foot powerboat. My fuel bill is less than 1/10 th his. I just ask him to save me room to anchor after he arrives. As the adage goes: its not about the destination, but the journey...
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Old 17-07-2017, 16:47   #21
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Fuel consumption - real world numbers

Quote:
Originally Posted by weavis View Post
I recently read an article regarding motor catamarans vs sailing catamarans in the med. I recall that when when the cost of sails, distance covered, speed over a set time were factored, the motor catamaran was cheaper to operate.



Go figure..


For smaller engined boats meant to run slower, that is true.
Only real justification for sail financially to me is once you want a boat to cover long distances.
I'm spending a bunch to refurbish everything sail related on my boat, chainplates, rigging and buying a new expensive sail and hardware.
What it's costing me to have that done would buy 10,000 gls of fuel. How long to do you think it would take me to burn that much fuel in a fuel efficient boat?
In my boat, thats 10,000 hours at normal cruise for me, 2000 RPM and 6.5 kts. 65,000 NM.
No you do the sail thing because you enjoy it, or have to have them, not because the make sense financially, how many sailing cargo ships do you see today? I know a lot of that is crew costs, but engines are just cheaper.
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Old 17-07-2017, 16:48   #22
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Re: Fuel consumption - real world numbers

I can't understand sailboats pottering at full speed....ok, it is about human nature, and Neanderthal habits maybe.

I hate going beyond 2000rpm, usually 1500rpm (Volvo tamd31 LA 130 bhp)
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Old 17-07-2017, 19:14   #23
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Re: Fuel consumption - real world numbers

We took a test trip in our 450 carver yoyager. 2 Cummins 450s. At 8 knots we got almost 1.6 mpg. At 18 we got .5. We did the trip at 8 and had a ball. Used $600 in fuel to go from Ky lake to Nashville. 390 miles and 9 relaxing easy days. It the only way we will travel from now on.
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Old 18-07-2017, 04:54   #24
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Re: Fuel consumption - real world numbers

Quote:
Originally Posted by weavis View Post
I recently read an article regarding motor catamarans vs sailing catamarans in the med. I recall that when when the cost of sails, distance covered, speed over a set time were factored, the motor catamaran was cheaper to operate.

Go figure..
That is interesting.
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Old 18-07-2017, 04:57   #25
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Re: Fuel consumption - real world numbers

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Originally Posted by a64pilot View Post
What it's costing me to have that done would buy 10,000 gls of fuel.
Wow! We could do the Great Loop two and a half times for that.
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Old 18-07-2017, 04:57   #26
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Fuel consumption - real world numbers

My Hunter 356 is a 2003 model I bought new. I have the standard 3GM30F Yanmar engine with a 5 KW Northern Lights generator. We run the generator continuous when not at the dock whether sailing, anchored, or motor cruising so we maintain conditioned space on our interior with the HVAC. I have a total of 1283 and 3143 hours on each, total of 4,426 total engine hours. We have sailed/motored 7,873 NM and 9,109 SM. Our average fuel burn including the generator is .83 gallons per hour and we assume .25 gal per hour for the generator so that makes the Yanmar .58 gallons per hour. Total fuel burned is 1,558.9 gallons. We generally cruise at about 6 knots, 75 to 80% RPM.

This yields a NM per gallon of 10.34 for the Yanmar alone and with the generator 7.2. We have a 38 gallon tank (actually hold 41.3 gallons) so without jerry cans we have a normal range of 273 NM with the generator. When cruising, we carry an extra 25 gallons on the rail and that takes our total range up to 453 NM just motoring.

When we are in the ocean cruising, we use 1 gallon per hour as our planned consumption when motor sailing with the generator. This accounts for currents, waves and the fact we are heavily loaded. We could forego the generator and extend our range by 43%, but my wife and I enjoy the amenities of heating and cooling and Dish network with our KVH antenna. We consider our boat very fuel efficient compared to some of our friends power boats. Of course, they can go to Mobile from Kentucky Lake in half the time we can, but their cost is very much higher than ours.
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Old 18-07-2017, 04:58   #27
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Re: Fuel consumption - real world numbers

Quote:
Originally Posted by Monepit View Post
We took a test trip in our 450 carver yoyager. 2 Cummins 450s. At 8 knots we got almost 1.6 mpg. At 18 we got .5. We did the trip at 8 and had a ball. Used $600 in fuel to go from Ky lake to Nashville. 390 miles and 9 relaxing easy days. It the only way we will travel from now on.
Good to know. We're looking at a Voyager for our next boat. Although, we're looking at the 46 Grand Salon version. Basically the same boat as yours.
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Old 18-07-2017, 05:37   #28
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Re: Fuel consumption - real world numbers

Had too include my 2 cents on fuel use
I too wrestle with my fuel use on my 31 ft Regal, 9 thousand lb boat
Has twin 4.3 gas engines

Retired , use boat too often .
Spending few days a week sleeping aboard , hanging at marina, going off shore fishing. Not a serious fisherman just like dropping a line
Try fishing off swim platform in rolling seas on a cruiser.
Not designed for fishing and no room along sides .
Boat is a weekender, beautiful with comforts of home with luxury cabin
MY WATER CONDO
A number of 100 mile round trips
Still burns 1 gallon a nautical mile .
Was advised prop re- pitching . Helped a lot , still burns fuel but gets up on plane lot faster engines not working as hard.
Some responses , run one engine yes, but adds hours on one engine and buyers questions WHY ?

I never cared about speed just the need too be on the water .
Most times I throttle around 10 rpms .
I really wanted a sail boat sailed many times.
Last year spent a week aboard a 40 foot Beneatau with a few guys . Lot of fun , Regatta was a lot of not fun work .
Knowing all the pit falls a power cruiser has , I caved on the great deal on cruiser plus wife has no sea legs and freaks .
Plan keep a year or two get my money back . YHEA wrong, presently had too have engines rebuilt . Manifolds & risers leaked water on too heads and having both engines rebuilt .

I have a 21 footer fishing boat and trailer at times too Marathon
Wife and I discussed how much fun it would be if we could travel few weeks by water too Marathon . I have a trailer for the big boat , which sweetened the purchase deal but trailering a 9 thousand lb wide beam ( have permits )boat not fun and the adventure is via water not RT 95 .

Marathon is around 320 miles each way by water from Cape Canaveral
apx 650 gallons EQUALS $ 8 trillion dollars

Next boat purchase within budget , not burning a lot of fuel ????? Challenge
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Old 18-07-2017, 07:56   #29
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Re: Fuel consumption - real world numbers

I've repeated this story many times, sorry
Ran into a couple on a 65' Viking last year in the Dry Tortugas and helped them with a problem they had and talked to the Capt they had hired to run the boat.
Now amenities wise my IP 38 is a country outhouse compared to their suite in the Hilton, so it is not a decent comparison.
But of course after seeing the engine room with those huge MTU's I had to ask about fuel burn and cruise speed. He said boat will go much faster but they usually cruise at 24 kts and burn 120 GPH. I had to absorb that.

They do go four times faster than I usually motor, but they burn 120 times as much fuel doing so, now they are at least twice the size boat I am, but 120 times as much fuel?
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Old 18-07-2017, 07:59   #30
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Fuel consumption - real world numbers

J Clark, I think your little Yanmar is using less fuel than you think, and that generator is using more.
My line of reasoning is my little 3.5 KW gen is supposed to use .25 gl an hour on average and I think can use as much as .5 if your pulling its guts out
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