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Old 04 August 2015, 04:25   #1
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Cruising distance - fuel planning

I know how much fuel my tanks hold and how much I use at a cruising speed. But wonder how much I need to keep in reserve for when I do longer distances.

Logically, I would assume enough to get to the next fuel supply, but how much extra on top of that to take into consideration variation in conditions / route / messing about ?

1/3rd, 1/4er, enough to get back to the start ?
What sort of variation do you get in usage if the conditions change ?

(where I am cruising there is very little boat traffic, so next to no chance of a tow)
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Old 04 August 2015, 04:31   #2
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The general rule is 1/3rd out, 1/3rd back & a 1/3rd in reserve. Saying that, I have been known to return on fumes before now, very stressful


.....sh1t happens.......
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Old 04 August 2015, 04:37   #3
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Bit like cave diving then. I'm actually tempted to run out just to see exactly how much fuel the tanks hold.

I've been told they hold 95 litres each, but I would like to know for sure.

If I do run out I assume I just top up and pump the rubber bulb on the fuel lines and all should be well ? (its not a diesel after all)

The other thing is the gauges never reach the full mark, they only show 3/4 full when I brim out the tanks - so I assume that when the show empty there is a 1/4 left. But that's only an assumption, one Id like to test for real.

I'm planning on going from Corsica to Italy, so I need to take it more seriously.
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Old 04 August 2015, 06:53   #4
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Quote:
Originally Posted by Trimix View Post
Bit like cave diving then. I'm actually tempted to run out just to see exactly how much fuel the tanks hold.

I've been told they hold 95 litres each, but I would like to know for sure.

If I do run out I assume I just top up and pump the rubber bulb on the fuel lines and all should be well ? (its not a diesel after all)

The other thing is the gauges never reach the full mark, they only show 3/4 full when I brim out the tanks - so I assume that when the show empty there is a 1/4 left. But that's only an assumption, one Id like to test for real.

I'm planning on going from Corsica to Italy, so I need to take it more seriously.
I don't know what your electronics setup is, but assuming that your engines are recent & you have a nmea2000 compatible plotter or gauges on board, I'd ditch the standard fuel gauges & go down the engine fuel flow route. There are a couple of threads kicking about at the moment regarding same. Way more accurate once you have it all setup. You might have to chuck a few quid at it to get it working, or you might already have the necessary bits installed to make it work & its just a case of setting it up.
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Old 04 August 2015, 08:21   #5
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Actually I do have them set up to show the fuel flow rate. So I know what its using as I go.

I just use the gauges to glance at when I cant do the maths in my head, or if I'm messing about and not at a steady pace.

Annoyingly cant seem to get the Garmin to show the range left, despite it knowing the size of the tanks and the rate being used.

When cruising I'm using 1.2 litres for one Nautical Mile - so I should get a maximum of 158 NM till I run out.

Italy is only 116 NM away - I should be fine then
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Old 04 August 2015, 08:26   #6
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Actually I do have them set up to show the fuel flow rate. So I know what its using as I go.

I just use the gauges to glance at when I cant do the maths in my head, or if I'm messing about and not at a steady pace.

Annoyingly cant seem to get the Garmin to show the range left, despite it knowing the size of the tanks and the rate being used.

When cruising I'm using 1.2 litres for one Nautical Mile - so I should get a maximum of 158 NM till I run out.

Italy is only 116 NM away - I should be fine then
A 25L can strapped to the deck as a reserve may make your day feel so much more comfortable
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Old 04 August 2015, 08:56   #7
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Your right. On the last long distance trip I took two 20l cans which fit very easily on one of the three lockers Ive got.

Never needed them, but it was nice having them along for the ride.

When I didn't take them every time I opened up the throttles and glanced at the fuel flow rate I got nervous. There are not that many marinas with fuel along the coast.

I could very easily store 4 x 20l cans without noticing it. But Two of them should give me an extra range of 30+ Nm.
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Old 04 August 2015, 08:59   #8
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Oh, the trailer mods are still working out great BTW:

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Old 04 August 2015, 09:30   #9
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Oh, the trailer mods are still working out great BTW:


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Old 04 August 2015, 20:13   #10
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Way to many variables to take into account. If Im correct and you are running twin engines your calculations are for good to reasonable conditions, if things become bad and you are punching big sea's obviously the consumption will increase. Slower speed causes more prop slip giving less range.

If one engine fails (fuel, mechanical or prop damage etc) will the boat still plane on one engine if so will it still do so in rough conditions. Most twin engine boats Ive been on don't perform very well under a single engine ( talking about cats and single v boats as my experience in twin ribs is limited).

Jon
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