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Fuel Mileage
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Author:  JeffK [ Wed Feb 18, 2009 8:49 am ]
Post subject:  Fuel Mileage
I know we don't have boats for the fuel mileage, but we are planning a boat trip, and need to guestimate the gas mileage.

I have a 2006 255 Sundowner with a VP 5.7 GXI-G, DuoProp. I have looked at simular boats, and it looks like 2.5 - 3 MPG. Does this sound about right?
Author:  Jim_R [ Wed Feb 18, 2009 12:52 pm ]
Post subject:  Re: Fuel Mileage
Cruising range varies by speed. This ought to help:

http://www.fourwinns.net/fastfacts/fastfact/2006/255S.pdf

But don't forget mitigating factors such as wind and currents! I'd think you'd want to plan for fuel reserves of at least 20%.
Author:  cougarcruiser [ Wed Feb 18, 2009 1:28 pm ]
Post subject:  Re: Fuel Mileage
You would probably cruise at about 8 gallons per hour and roughtly 25mph. Give yourself a nice buffer and you are comfortably 2.5-3 miles per gallon.

I am with Jim - I would assume the safe side of 2.5.
Author:  ardy [ Wed Feb 18, 2009 8:00 pm ]
Post subject:  Re: Fuel Mileage
I tend to work on litres per hour which in my H180 3.0 is about 10 to 12 litres per hour or 2 and a bit gallons per hour roughly
Author:  ardy [ Wed Feb 18, 2009 8:02 pm ]
Post subject:  Re: Fuel Mileage
And I find running on the plane at about 3 to 3 and a half thousand revs to be the most fuel efficient as a general rule
Author:  JeffK [ Wed Feb 18, 2009 8:18 pm ]
Post subject:  Re: Fuel Mileage
Thank's, that's normally how I cruise, 3000rpm @ 29mph Trimming and tabing for optimum performance. I have a fuel meter on my wish list.
Author:  Obie [ Thu Feb 19, 2009 2:51 pm ]
Post subject:  Re: Fuel Mileage
I also have a 255 with a 5.7 liter GXI. I have a fuel flow meter and get 2.8 to 3.1 miles per gallon. My speed vs fuel efficiency values are very similar to those provided by FourWinns when I purchased the boat. I boat mainly at an elevation of 6100 ft and need to use an F3 prop set. You may be more efficient at a lower elevation and with an F4 prop set. I am most efficient at 3200 RPM. If you want to stretch your miles, get a GPS so you know your speed to a tenth of a mile per hour and work with the outdrive trim and the trim tabs. I can usually get a few more miles per hour at the same RPM by tweaking the tabs.
Author:  powellcrazy [ Thu Feb 19, 2009 8:46 pm ]
Post subject:  Re: Fuel Mileage
LOL :lol: :D

You guys make it sound like your cruising across the country and have no budget!

I do try to trim for optimum, but somewhere the fun factor out weights the economy! Enjoy the ride and scenery and worry not about one tenth of a gallon of fuel per hour, its not worth it. Seriously though, I do have a fuel flow meter on my wish list of upgrades for the boat.

I have found that FW posted mileage ranges to be fairly on the money, but I try to stick with the 1/3 rule. 1/3 out, 1/3 back, 1/3 reserve.
But of course I only learned this the hard way by running out of fuel a few times, because I knew how to read the gas gauge.

Happy boating!
Author:  ht32bsx115 [ Fri Feb 20, 2009 2:33 am ]
Post subject:  Re: Fuel Mileage
Around 3 mpg is not uncommon for medium size 18-22ft I/O boats.

I put a Lowrance fuel flow gage in my 87 lib when I installed the 454 and with the 26p props I get 30 mph at 3000 rpm. Fuel flow is right at 10gal/hr. (to get mpg with one you must have GPS interfaced with it)
Image

When I push it up to 45 mph fuel flow goes to about 15 gal/hr. (still about 3mpg)

Some small outboard boats with newer 4 stroke and DFI (ETEC) 2 stroke engines will do far better. A recent test in Trailerboats had a 50hp (Honda I think) engine doing almost 10 mpg.


Dual counter-rotating props will get better mileage than single prop drives...


Cheers,


Rick
Author:  jvalich [ Fri Feb 20, 2009 6:18 am ]
Post subject:  Re: Fuel Mileage
Generally, 75% of your WOT rpms is considered the "sweet" spot. Of course, a fuel flow meter is the best way to get your best economy. It is one of the few items you can install on your boat that will provide a ROI.

Please remember what we teach in the USPS regarding fuel... the 1/3 rule. I/3 there, 1/3 back and 1/3 reserve. I don't know where you will be boating but fuel consumption can change greatly in snotty water conditions.

Above all... enjoy!
Author:  Jim_R [ Thu Mar 05, 2009 4:51 am ]
Post subject:  Re: Fuel Mileage
jvalich wrote:
Please remember what we teach in the USPS regarding fuel... the 1/3 rule. I/3 there, 1/3 back and 1/3 reserve. I don't know where you will be boating but fuel consumption can change greatly in snotty water conditions.

Above all... enjoy!


That's what I was trying to get at with my reserve suggestion. If you're planning an extended cruise, I'd even take it so far as to plan alternate fueling stops and plan for fuel reserves on top of that. I have a paddle on my boat, but I never want to have to use it.
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