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Old 18 March 2010, 08:29   #1
Country: UK - Wales
Make: Osprey
Length: 7m +
Engine: outboard
Join Date: Oct 2004
Posts: 66
Another fuel consumption question.

I will be providing support to a long distance event where the competitors will be averaging 6-8 knots.

There may be the odd 5 minute blast but the rest will be at slow speeds.

The event is about 90 miles without a stop (or refuelling points) so are looking at 15hrs on the water, and I am trying to calculate the fuel requirements for a mariner 40 2 stroke and a suzuki 60 4 stroke. We know the fuel at WOT and crusing but not at slow speeds.

Do I just take the same fuel with the reduction in speed and increase in time leveling out to the same consumption?

Perhaps Mr ex Barrus could help with the Mariner as that's where it came from!

Advice greatfully received!

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Old 18 March 2010, 08:43   #2
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,538
This is a bit of a "touchy feely" reply, but I once ran a Mariner 40 2-stroke on the back of an SR4 duting the Oppie nationals and managed something like between 9am-5pm on 3/4 (ish) of a 5 gallon tank - 6 days in a row (as in 3/4 tank / day!) . Like you suggest, a lot of tickover pootling, and a few blasts to / from the course & when someone capsized.

Can't be a lot of help on the 4- stroke I'm afraid.

The trick for stuff like that is to switch off when not moving, and if you're lucky, the tide / wind will work in your favour as well! Also if you are on premix with the mariner, will stop it oiling up.

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Old 18 March 2010, 10:18   #3
Country: UK - England
Town: bicester
Length: no boat
Engine: outboard only
Join Date: Feb 2009
Posts: 851
I cant help with your 60hp but rule of thumb for the 40 hp is 2/5 of the hp in litres per hour at wide open throttle please remember all fuel consumption figures are approx weather boat and many facters have to be taken into consideration err on the side ofcaution and good luck
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Old 18 March 2010, 12:09   #4
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Country: UK - Channel Islands
Town: A large rock
Boat name: La Frette
Make: Osprey Vipermax
Length: 6m +
Engine: 200 Suzzy
Join Date: May 2004
Posts: 2,796
I've acted as guard boat a couple of times for a rowing race. On each occasion there was a 10kt 15 mile outbound journey towing the rowing pair, and then a slow 6 to 8 kt return. With both a Suzuki 90 and 200 on different occasions my overall fuel consumption was less than a normal day of blatting around. Will look and see if I've got any consumption figures. On neither occasion was I on the plane at those speeds.
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