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Old 13 September 2008, 03:05   #1
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MPG 150 HP Evinrude and 6 m Rib

Very general question but if I was messing around for say 4 hours in a 6 M rib with 150 HP stroke how much fuel woudl you think was reasonable to use

For me Messing around woudl mean a a lot of speed and some towing

I am about to buy a new boat and I am keen to ensure I dont have to refuel every day so want to get something like the right sized tank

I know this is a bit like "how long is a piece of string" but I am thinking circa 100 litres

Also would a 4 stroke be better from a consumption view point
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Old 13 September 2008, 04:49   #2
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I am thinking circa 100 litres
sounds more like 4 hours cruising than 4 hours at top speed.
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Old 13 September 2008, 05:11   #3
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a 100 litre tank is a bit small. Cruising you'll be using roughly 1ltr per Nm, that''ll give you a workable cruising range of 80-90 miles which is surprisingly little. A good run up the coast and back could put you on the limits of your range. My 6.5 Osprey had a 180ltr tank, my current boat 220.
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Old 13 September 2008, 08:08   #4
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sounds more like 4 hours cruising than 4 hours at top speed.
Agreed, my 150hp could easily get through 100l in under 2 hrs at wide open as I'm sure everyone else's would. I get about 25 l/h at 'economy' cruising of around 25-6 kts. So that's 4hrs. Mind you, that's quite a bit of range; 100+nm for a day out.

My own tank is 150l and I'd personally think that is a sensible minimum for a 150hp. Using the usual safety guide of 1/3 out, 1/3 return and 1/3 spare it's really a 100l usable before eating into the 'reserve' margin. However, if you are just bombing around the Solent you probably don't need to be quite so generous on the reserve.
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Old 13 September 2008, 10:22   #5
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I doubt you'll get any better than 1lt per mile from an average outboard, more realistic is 1.2 lt per miles at cruising speed. My DI sucks up fuel at the rate of 65 lt per hour at WOT! With my Tank which is 200lt this gives me a workable range of 150 Nmiles to include a 10% margin.

Get the tank size wrong now and you'll regret it forever, so go for the biggest tank you can, you don't have to fill it to the brim every time, but the capacity is there if you need it.
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Old 13 September 2008, 11:34   #6
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I'd second going for the largest tank you can fit. The in console tank on my Humber probably holds about 80L though the fuel gauge is not very accurate (it shows less than there actually is I think/hope!) but the range is really quite restrictive. I carry about 60L of fuel in cans on the boat, but refuelling at sea is a PITA unless it is absolutely flat calm, and I'd much rather have a 150L tank and forget about the cans... mind you my old clunker burns about 1.2L/nm (oh for an Etec ) so that doesn't help. If I ever replace it with something of a similar size I wouldn't go for less than a 150L tank. You can always run a 150L tank with 100L in if you need to cut down on weight, but its hard to do it the other way round
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Old 13 September 2008, 14:12   #7
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I doubt you'll get any better than 1lt per mile from an average outboard, more realistic is 1.2 lt per miles at cruising speed. My DI sucks up fuel at the rate of 65 lt per hour at WOT! With my Tank which is 200lt this gives me a workable range of 150 Nmiles to include a 10% margin.

Get the tank size wrong now and you'll regret it forever, so go for the biggest tank you can, you don't have to fill it to the brim every time, but the capacity is there if you need it.
Agreed about the tank size. You don't have to use it, but at least you know its there if you need it.

Consumption depends hugly on how you drive. Used 122l on Revo yesterday(6.5m, 175 Evinrude). Did roughly the same day again today and used about half (drove like a nutcase yesterday and very conservatively today)
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Old 13 September 2008, 15:18   #8
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Thanks

Thats to all of you for the replies

So without doubt I am hearing... get as big as you can

What says you on 4 stoke or 2 stroke in terms of MPG or indeed any other view?
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Old 13 September 2008, 16:02   #9
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Jon,

I am running a 150HP Etec (2stroke) on the back of a 6.5 I get about .9 litres per mile when crusing at 20-25 knots then at WOT about 54 litres per hour.

If you buy a modern 2 stroke or 4 stroke and ensure it is propped right then you should be able to achieve the same.
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Old 13 September 2008, 17:46   #10
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I wouldn't buy another large 2 stroke, simply because buying and filling oil is such a pain.
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