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Old 07-23-2015, 01:28 PM   #1
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OA 423 Classico Fuel consumption tates

Can anyone on this forum give me fuel consumption rates for a 423 Clasico with twin 330 Cummings engines?

I am thinking of buying a 423 Classico, but most seem to have the larger engines. I'm hoping to keep fuel consumption at 4/5 gallons per hour. Is it possible to get this fuel consumption running hull speed on one engine?

Thanks in advance for your answers.

Gordon
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Old 07-23-2015, 03:10 PM   #2
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Gordon:


If by larger engines you mean the 370 hp Cummins or even the larger displacement 6CTAs of 450 or so hp, you really won't see a meaningful fuel consumption difference among them, maybe a half gph more for the Cummins C, but no difference among the Bs.


Here is a way to estimate fuel consumption at hull speed. Take your displacement and multiply by .0015 for a displacement hull and .002 to .0025 for a semi displacement hull. Lets use 40,000 lbs and the higher semi displacement factor and you get 100 hp to reach displacement speeds.


Divide that by 17 (for a Cummins B or QSB, a point less for a Cummins C) and you get about 6 gph for the Cummins 330 hp engines at hull speed. If you slow down a knot you will hit your 4-5 gph target.


FWIW the .0015 factor is developed from looking at data from Voyaging Under Power by Bebe/Leishman. The .002-.0025 factors are educated guesses. The 17 and 16 factors are taken from the prop fuel consumption curves for the Cummins B and C engines at the low end of the curves.


David
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Old 07-23-2015, 09:28 PM   #3
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David,

Thanks for the reply. The engines are m10TAs rated at 330 each.

Gordon
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Old 07-23-2015, 09:41 PM   #4
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One more question

Dave,

Can I cut consumption by running On one engine? The Claudio weighs in at 34200. If i understand the math, we could get 4.5 gall/hour. I guess it makes no difference if one or two engines running?

Thanks again,

Gordon
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Old 07-23-2015, 11:36 PM   #5
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Dave,

Can I cut consumption by running On one engine? The Claudio weighs in at 34200. If i understand the math, we could get 4.5 gall/hour. I guess it makes no difference if one or two engines running?

Thanks again,

Gordon
I think your boat at 7 knots would likely hit 4.5GPH...that is a total WAG on my part but I think it would be very close. I also think you would cut another .5GPH off by running on one engine. There are numerous posts on this forum about running on one engine in a twin engine boat. Do a search. There are things that need to be considered....like whether your transmissions can free wheel without causing damage.
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Old 07-23-2015, 11:47 PM   #6
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some good info here

Sometimes big engines are an advantage

Here we go again !!
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Old 07-24-2015, 07:37 AM   #7
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The manufacturer may claim that it weighs 34,200 lbs dry, but that boat is similar to a GB 42, so it probably weighs closer to 40,000 loaded with fluids, gear, people, hull water absorption, etc.


As Baker noted you can probably pick up 1/2 gph while running on one engine. But you have to make sure that your transmission can freewheel safely and it will also affect low speed handling. I wouldn't bother.


David
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Old 07-24-2015, 11:18 AM   #8
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As Baker noted you can probably pick up 1/2 gph while running on one engine. But you have to make sure that your transmission can freewheel safely and it will also affect low speed handling. I wouldn't bother.
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Old 07-24-2015, 11:36 AM   #9
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Your boat is very similar in hull design to my C&L 44. mine weighs in at 44000 lbs, fully cruise ready. I usually go 8 knots and use 4 gph. You can too. I do this on 2 engines, as I don't believe the theories about getting more efficiencies from running one engine harder while pushing the boat from one aft corner while dragging a 23 inch 3 blade brake through the water.
What I do believe is that your fuel efficiency is directly related to the size of the stern wave you are making, so keep your eye out behind you.
The size of your equipment really doesn't matter in this analysis.
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Old 07-24-2015, 12:15 PM   #10
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I am thinking of buying a 423 Classico
Gordon
I'm also looking at one in Florida. I see there's one in Virginia as well. Are you looking at that one? I'm not familiar with the boats at all. Do you know much about them, positive or negative?
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Old 07-24-2015, 01:32 PM   #11
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Gordon: The ratings have nothing to dowith fuel consumption except at WOT and you cant run there for long.. The weight of the boat and how fast you go determines that. A 40,000 # boat will get between 2-3 NMPG at 5 to 8 knots. Your pick.
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Old 07-26-2015, 10:22 AM   #12
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Kalakai,

I looked at the one in Virginia and frankly was disappointed. I think the Owner wanted way to much for the boat. I am just starting the search and May change my minds as I go. I found the boat not was nor as squared away as I would have hoped, from a cleanliness and tidyness punt of view. The hard top was in great condition as was the flybridge enclosure.

It seems to Me that OAs offer a lot for the money, burr I am a novice at this and May change my mind as I go.

A friend in my Marina bought the 423 last fall and he is seriously thrilled with his 1995 model. I love the Big fly bridge And the sturdiness of the boat.

I would love to learn more if anyone has any insights as to pros and cons of OAs.

Gordon
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Old 07-26-2015, 11:23 AM   #13
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I would love to learn more if anyone has any insights as to pros and cons of OAs.
Well, I'm sure that everyone expected me to respond to this thread.

Things I love about my OA....

1) Semi displacement hull gives me a nice ride when on plane.
2) Interior wood is extremely well done.
3) The hard top on the fly bridge is such that you could hold a dance on it.
4)The guest room (twin side X side births) is terrific!
5) The fly bridge is huge! Maybe it's too big!
6) Sound proofing in the ER is great! (Can hardly hear the genny.)
7) Side door to cockpit is a huge help when provisioning.
8) Salon is spacious with big windows.
9) The damn boat is very good looking and everyone says so!
10) At 42', it has everything I want and the monthly bill is affordable.

THE BOAT IS SOLIDLY BUILT, DOESN'T CREAK OR GROAN WHEN COMING OFF A WAVE & IS NOT WET.

Here's a sister ship at speeed.
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Old 07-30-2015, 08:54 AM   #14
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Kalakai,

I looked at the one in Virginia and frankly was disappointed.
Gordon
I was interested in that boat as well, but the 6k hours on the engines is too much for me.

I was also looking at a '96 in Florida, but was told by someone who checked her out that she looks pretty rough for her age, especially for the price. The other issue is she has CAT 3116 engines, which have a terrible reputation. Whether it's deserved or not, it significantly affects resale value. I've been reading up on them at boatdiesel as well as talking to local mechanics. Story ranges from "run, don't walk away from any boat that has 3116s" to "they're great engines if properly maintained, correct oil is used, and not pushed too hard".

cheers & good luck
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Old 08-02-2015, 06:11 PM   #15
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Still stumped

I looked at the O A Classico 423 today, And other than hundreds of gelcoat cracks think it might be a buy..... Still, i have no idea what its fuel consumption might be at hull speed. The previous Owner throws around numbers like 15 gallons at 16 knots, but that is not helpful. The boat has turbo charged Cummins 330 hp engines. A friend with a ckassico 423 gets 4 gph with twin 220s. I have done The math, but wonder if anyone else On this forum might have this configuration And know The numbers. I really want a boat that stays at 5 gph or less at hulk speed. Its this the wrong boat?

Gordon
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Old 08-02-2015, 06:42 PM   #16
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I looked at the O A Classico 423 today, And other than hundreds of gelcoat cracks think it might be a buy..... Still, i have no idea what its fuel consumption might be at hull speed. The previous Owner throws around numbers like 15 gallons at 16 knots, but that is not helpful. The boat has turbo charged Cummins 330 hp engines. A friend with a ckassico 423 gets 4 gph with twin 220s. I have done The math, but wonder if anyone else On this forum might have this configuration And know The numbers. I really want a boat that stays at 5 gph or less at hulk speed. Its this the wrong boat?

Gordon
The numbers seem to sort of look like this, as general rule of thumb.

Best case mpg single engine trawler is something like a MainShip 34' at 7 tons/ 7 kts/ 2 gal hr/3-4 mpg.

Anything bigger with twins is going to chug along slightly faster at 8 kts giving 2mpg or there abouts.

The difference between 6, 7 and 8 kts is enormous in terms of fuel consumption, but remember with twins you will have run above minimum idle revs or the engines bores will glaze, so that's why 8 kts is normal cruise speed .

Those numbers seem to cover most trawlers under 50'.
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Old 08-02-2015, 08:54 PM   #17
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Classification please

Peter,

Thanks for the response. Are you a Mechanic or engineer? How often would I need to run the engine up to prevent glazing and for how long?

If I understand your response, i should burn less then five gallons an hour at hull speed.

Again thanks for the help. I am Perry knowledgeable about sailboats, but trawlers are a new species for me.

Gordon
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Old 08-02-2015, 11:42 PM   #18
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Gordon, glazing of bores usually comes from engine underloading, like extended unnecessary idling. It doesn`t relate to the frequency of running an engine.
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Old 08-03-2015, 05:23 AM   #19
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Peter,

Thanks for the response. Are you a Mechanic or engineer? How often would I need to run the engine up to prevent glazing and for how long?

If I understand your response, i should burn less then five gallons an hour at hull speed.

Again thanks for the help. I am Perry knowledgeable about sailboats, but trawlers are a new species for me.

Gordon
Hi Gordon,

I grew up on a tillage farm, and we had two tractors; ploughing tractor and runabout tractor . the little Ferguson 135 belched smoke and couldn't pull the skin off a rice pudding and was left idling for hours at a time; it was rebuilt several times with only 3000 hrs on the clock. The big tractor used for hauling big tailers and ploughing was never rebuilt,and had thousands and thousand of hours usage with no problems.

The inside of a cylinder is not smooth, its honed with a cross hatch pattern to retain lubrication oil as the piston goes up and down. At low loads there's low heat which means a lot of soot and carbon is produced clogging up the honed surfaces, so no oil is retained on the honed surface .....causing massive wear, blow by of the compression gasses, and early failure of the engine.

Diesel engines like 3/4 load ( calculated from 3/4 fuel consumption figures).

From my personal experience you can get away with 1500 revs without problems if you give the engine a bit of a blast under load every so often: running your engine at idle for extended periods will kill it.
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Old 08-03-2015, 12:26 PM   #20
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Peter,

Thanks for the response. Are you a Mechanic or engineer? How often would I need to run the engine up to prevent glazing and for how long?

If I understand your response, i should burn less then five gallons an hour at hull speed.

Again thanks for the help. I am Perry knowledgeable about sailboats, but trawlers are a new species for me.

Gordon
I own those exact same engines. I do believe the manual says that you should run those engines up to a "proper" load 1 out of every 8 hours. So 1/8 of the time.

And I agree with Peter's assessment. Your fuel burn will be very similar to your Buddy's with the twin 220s. They are basically the same engine. And you are using the same horsepower to go the same speed in the same boat. So the numbers will be very close.

Think of those engines as thoroughbreds. Would it be healthier for a horse to stay pinned up or to let her out and run every now and then. Lets those engines eat every now and then. They love to run!!!
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