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Old 07 June 2011, 11:50   #1
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Fuel Consumption vs Tube Pressure

Hi,
Another daft question;

Whilst still looking for a new outboard, I installed a new fuel gauge and noticed I am burning far too much fuel compared to say January. The rib is moored on the water.

I have never topped up the air pressure and the tubes are not as firm as they used to be.

So have you guys experienced increase in fuel consumption whilst the tube pressure is lower?

when I mean increased fuel consumption is like burning 50% more...
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Old 07 June 2011, 12:24   #2
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Do your tubes actually contact the water when you're underway?
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Old 07 June 2011, 12:32   #3
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The hull isn't covered in weed and other such rot is it? I can't imagine squishy tubes being half as fuel efficiency harming as a layer of wildlife being dragged along
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Old 07 June 2011, 12:52   #4
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Quote:
Originally Posted by Leapy View Post
Do your tubes actually contact the water when you're underway?
Yes, the rib being good old Humber it always touches the water. So maybe when the pressure is a bit lower, it is touchinng more?!!!


Also, do you guys know what's the normal psi level of the tubes? I am buying a pressure gauge to check this.
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Old 07 June 2011, 15:26   #5
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Is your hull antifouled and if so when was it last recoated?
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Old 07 June 2011, 17:34   #6
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Yes, sounds to me as if you've got some growth on the bottom. If you've antifouled the hull, did you do the tubes too? If not, you need to. I've done mine for the last four years and it seems ok. Internationals 'Navy' is exactly the same colour as my Humber's tubes and you can't see the join.
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Old 07 June 2011, 18:04   #7
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I have never topped up the air pressure and the tubes are not as firm as they used to be
erm...pump em up and try it ?
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Old 07 June 2011, 18:24   #8
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Quote:
Originally Posted by Vandad View Post
Hi,
Another daft question;

Whilst still looking for a new outboard, I installed a new fuel gauge and noticed I am burning far too much fuel compared to say January. The rib is moored on the water.

Is the increased fuel consumption as read on the new fuel guage, or actual use?
If you're judging this on the fuel guage reading - are you sure the new fuel gauge is accurate? It may not be coincidence your "increased consumption" has happened after installing a new gauge

I'd full her up, go for a run or two, fill her adain and see how much fuel she uses per NM/ hour based on the usage between top ups.

Many fuel guages are veet inaccurate. could it be a problem with the sender in the tank?
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Old 08 June 2011, 04:41   #9
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A friend of mine ruined an end cone on a zodaic rib by not inflating the tubes to the correct pressure (At least this is why the end cone failed according to the repair guy (inland inflatable services in sligo)) He has a good rep as far as I can tell. So keep those pressures right or it could cost you more than just additional fuel

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Old 08 June 2011, 05:04   #10
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Originally Posted by two stroke mick View Post
A friend of mine ruined an end cone on a zodaic rib by not inflating the tubes to the correct pressure
Yes, low pressure is very sore on tubes. It causes the tubes to ripple and twist violently underwater. This can lift tapes and remove rubbing strakes if the conditions are bad enough and the speed high enough.
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