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 fuel burn for a 43' Mainship?
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Cobalt 25

USA
1030 Posts

Posted - Mar 23 2010 :  21:54:11  Show Profile  Reply with Quote
Last week we rented a 43' Mainship with 315hp Cats. While refueling at the end of the trip, the marina ran out of diesel after only 40 gallons into one of the fuel tanks. They claimed that the 500 gallon reserve at the bottom of their tank prevented dirty fuel from reaching the customer, but that's not the issue.

Not having a clue to diesel engines, I'd like to get an estimate of how much fuel we burned so that we'll have a ballpark idea when they tell us how much $ we owe. We cruised at about 1800 rpms through seas that mostly averaged one to two feet for approximately 130nm. However, the last 40nm were a little sporty with 4-5 foot beam seas.

Add to that the diesel genny that was run for maybe 10 hours.

Your best educated guesses on total gallons burned?

Thanks, Peter

Peter Haviland

The Other Gary

Canada
8609 Posts

Posted - Mar 23 2010 :  22:04:15  Show Profile  Reply with Quote
based on my twin cummins and genny 150 to 160 gallons.


Gary Peck 1997 Bayliner 3988 MY, twin 330 Cummins

I saw a movie where only the military and the police had guns,,,,, It was called Schindler's List
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JLC

USA
1195 Posts

Posted - Mar 23 2010 :  22:29:33  Show Profile  Reply with Quote
I see your from the Cape. Did you rent from the Cape area or NH?

If I can ask......How long did you rent for and how much do they charge?

Other than the fuel.... how was the boat and the over all experience of renting?

Thanks.


Edited by - JLC on Mar 23 2010 22:31:52
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Cobalt 25

USA
1030 Posts

Posted - Mar 23 2010 :  22:49:40  Show Profile  Reply with Quote
We were fortunate enough to rent out of Key West- a lot less snow than here at my house in Vermont!

We rented for a week at (I think) $5500. The boat was not a Bristol beauty queen but a lot of fun. Three cabins for my wife, sister, my niece and nephew and their 2 sons- all in 3 cabins. Handling twin screws for the first time was exciting, especially with stronger-than-expected Florida currents and a bit of wind.

Overall experience? Awesome. I sometimes think I want to spend the rest of my life on a boat!

Peter

Peter Haviland
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rbmitchell

Billie Baird
2176 Posts

Posted - Mar 24 2010 :  04:51:50  Show Profile  Reply with Quote
That boat weighs about 37,000 pounds while The Other Gary's weighs about 21,000. I think you would tend to run about 30% more fuel burn per mile although about the same burn per hour. You just run a little slower because you're so much heavier. My guess would be closer to 200 gallons or $700 at Key West.

The generator would burn only one gph flat out so that's fairly insignificant.

Who in Key West rented the Mainship? I spend Februarys there. Any idea how fast you were running at 1800 rpm?

"The solution to this problem, when found, will be obvious."
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gerrys

69 Posts

Posted - Mar 24 2010 :  05:08:45  Show Profile  Reply with Quote
at 1800 rpm approx .9 to 1.0 statute mpg (displacement at about 9-10mph)
at 3400 rpm approx .5 to .6 mpg (on plane about 24 mph)
these are actual with twin yanmars.

Edited by - gerrys on Mar 24 2010 05:10:11
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dominic

1282 Posts

Posted - Mar 24 2010 :  06:54:49  Show Profile  Reply with Quote
Which model CATS? CAT publishes fuel burn specs over a range of RPMs.

For your comparison, I run a pair of fully mechancial 350 HP CAT 3126-TA motors in a 41 express cruiser (~45' LOA) that has a dry weight of ~23000 lbs....add 2-3K lbs fully loaded.

I don't have fuel flow meters for instananewous fuel burn numbers. However, I keep very accurate logs of hours and distance traveled and then chart according to the fuel burned based at fill ups. I 'Average' 1.0-1.1 sMiles per gallon. That's an average fuel burn which includes ~60-70% of the travel on plane at ~2300 RPMs.

later,
dominic
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pdecat

USA
36961 Posts

Posted - Mar 24 2010 :  07:23:37  Show Profile  Reply with Quote
Taking Bobs weight estimate into consideration my guess is a lot more like 200 gal depending on how much of your run was at planning speed

Bruce


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vic33004

USA
1557 Posts

Posted - Mar 24 2010 :  08:28:15  Show Profile  Reply with Quote
if you say how many hours you were running at 1800, there is a fuel use curve available for that engine that will give you a pretty good idea how many gallons per hour they burn.

Vic33004

02 Regal 4260
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Cobalt 25

USA
1030 Posts

Posted - Mar 24 2010 :  08:29:07  Show Profile  Reply with Quote
rbmitchell, Florida Yacht Charters (305) 532-8600, a very rough guess of 10-12mph rb2rb2@gr5tgr5t 1800rpms.

dominic, no idea of model of Cats, in fact, it MAY actually be the 350 hp model

pdecat, you know, it didn't seem like we ever got on plane. I'm used to a 26' Formula, THAT gets on plane!

thanks for all your help!

Peter Haviland
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Ghost

USA
6707 Posts

Posted - Mar 24 2010 :  08:49:46  Show Profile  Reply with Quote
You were on plane. Figure 1mpg

What part of GALE WARNING did you not understand?
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van lafermine

USA
488 Posts

Posted - Mar 25 2010 :  09:45:26  Show Profile  Reply with Quote
It seems that the guestimates are all over the place. Why dont we do a over and under?

130nm travel
snotty conditions
1800 rpm
10hr. gen time.
37k # boat

My vote over 175 gl.

Let us know what the final # is once you get the bill..

Van
"Drifting Profits II"
4460 Regal
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Cobalt 25

USA
1030 Posts

Posted - Mar 25 2010 :  10:18:38  Show Profile  Reply with Quote
Roger that.

She should be contacting me fairly soon. If she comes in with 400 gallons she has some explaining to do! I'm hoping for about 14 galons (:

I'll keep you posted.

p.s. I have no reason to disbelieve her, she's been a straight shooter. I just don't want to be completely in the dark.

Peter Haviland
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Gregory S

USA
11980 Posts

Posted - Mar 25 2010 :  11:52:46  Show Profile  Reply with Quote
I guess the bottom line here is that you used whatever they claim you used.
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vic33004

USA
1557 Posts

Posted - Mar 25 2010 :  14:04:09  Show Profile  Reply with Quote
a friend of mine has a 46 searay express with similar weight to your mainship and cruises at about 18 knots with cummins 6CTA's. to run from fort lauderdale to key west is about 150 miles and he will burn approx. 250 gallons doing that. the sea state has little influence on the burn rate unless you are slowing down in a big way and dragging the sea. the genset burn is of little consequence as they are rarely loaded, you might have used about 1/2 gallon per hour of use on the genset.

Vic33004

02 Regal 4260
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rbmitchell

Billie Baird
2176 Posts

Posted - Mar 25 2010 :  16:49:45  Show Profile  Reply with Quote
The Caterpillars in that boat could be 3116 or the 3126. Both are inline sixes and rated between 300 and 350 hp. 1800 is a poor rpm for those engines. They are rated at 2800 or 3000 rpm and should do best at 2400 rpm for economy and life.

Why 1800? Did SWFY tell you not to esceed that?

"The solution to this problem, when found, will be obvious."
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dominic

1282 Posts

Posted - Mar 25 2010 :  17:28:07  Show Profile  Reply with Quote
Here's the published fuel burn numbers for a 300 HP 3116-TA motor. Multiply by two. In my personal experience, I have found the CAT published numbers to be quite accurate.



later,
dominic

Edited by - dominic on Mar 25 2010 17:28:56
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Cobalt 25

USA
1030 Posts

Posted - Mar 25 2010 :  18:45:58  Show Profile  Reply with Quote
rbmitchell, no one suggested 1800 rpms. I believe she said 1100 or 1200 rpms gave the best fuel economy. Way too slow. A printed note either on the helm or in the engine room said, "Do not exceed 2,000 rpms for over an hour at a time". Not knowing anything about diesels, 1800 "felt" O.K. to me. I guess it wasn't.

dominic, thanks for your chart. Without knowing the hours we operated, is it possible to calculate the fuel consumed?

Peter Haviland
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Audrey II

USA
8959 Posts

Posted - Mar 25 2010 :  19:05:50  Show Profile  Reply with Quote
[quote]Originally posted by dominic

Here's the published fuel burn numbers for a 300 HP 3116-TA motor. Multiply by two. In my personal experience, I have found the CAT published numbers to be quite accurate.

Can you send me a link to the chart for the cat 3126ta turbo 420hp. I have been saying I get about a mile per gallon and no one believes me this info sounds dead on. I cruise at about 2400 doing about 20 miles per hour and burning about 20 gallons per hour this seems inline with the data that has been stated here I would love to see the chart.

Dave

“Time you enjoyed wasting is not wasted time.” – T.S. Elliotcommon.
-----------------------------------------------------------

1996 440 Trojan Express

Edited by - Audrey II on Mar 25 2010 19:15:45
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dominic

1282 Posts

Posted - Mar 25 2010 :  19:37:01  Show Profile  Reply with Quote
Dave

I sent you a PM....

later,
dominic
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Audrey II

USA
8959 Posts

Posted - Mar 25 2010 :  23:11:38  Show Profile  Reply with Quote
Thank you but I didn't get it.

Dave

“Time you enjoyed wasting is not wasted time.” – T.S. Elliotcommon.
-----------------------------------------------------------

1996 440 Trojan Express
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dominic

1282 Posts

Posted - Mar 26 2010 :  04:55:50  Show Profile  Reply with Quote
Dave:

When I click on your RO name and then click to send a PM to you, it comes up with an invalid RO name in the PM box. I didn't realize that. Maybe Les can fix that for you.

Anyway, I sent another PM with a corrected name...let me know if you get it...


in the mean time, below are the basic fuel burn numbers for the 420HP version...based on your numbers above....cruise 20 sMPH at 2400 RPM and using the fuel rate burn from the chart below of 13.3 GPH (each) at 2400 RPM, you're fuel mileage is .75 sMPG at cruise. However, it is very likely that you AVERAGE 1.0 sMPG overall...








later,
dominic
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abalmuth

USA
6180 Posts

Posted - Mar 26 2010 :  06:22:59  Show Profile  Reply with Quote
quote:
Originally posted by dominic

..., I have found the CAT published numbers to be quite accurate.

I agree with Dominic, the Cat numbers are very close +or– 5%

Dave
I have been a member of the Boatdiesel web site for years and as good as it is Cat’s updated web site has very good information
http://marine.cat.com/propulsion/legacy
They also have a forum

Carver Voyager 530 with Volvo 122's/610HP
Light travels faster than sound. This is why some people appear bright
until you hear them speak.........
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Audrey II

USA
8959 Posts

Posted - Mar 26 2010 :  07:20:43  Show Profile  Reply with Quote
Thanks guys

Dave

“Time you enjoyed wasting is not wasted time.” – T.S. Elliotcommon.
-----------------------------------------------------------

1996 440 Trojan Express
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