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Old 26 August 2014, 08:59   #1
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Engine drinking way too much fuel for my liking

I currently have a 135 V6 on my rib and although I knew it would drink the fuel at WOT I thought it may be more frugal at a slower speed.

Went to yarmouth from calshot last Sunday and back just at a nice steady pace of the region of 20kts and ended up using about 50 litres of fuel with 2 adults and a dog.

Boats in general are not cheap things to run but I was hoping for better consumption than I have currently.

Especially as the fuel tank on board my boat will not allow me to go much further than yarmouth without running out of fuel.

Would a smaller engine I.e 100hp or 115hp be really that much better or are all engines just absolute abysmal on consumption.

And should I just accept being skint if I want to run the boat
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Old 26 August 2014, 09:14   #2
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Something not right say you did 25 miles that's 2lt per mile you should be getting better than that, what is the engine?
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Old 26 August 2014, 09:23   #3
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I have a 150 v6 and on a good day I'll burn 1.1 ltrs per mile but if it toughs up it does go up can jump up considerably depending on throttling.


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Old 26 August 2014, 09:54   #4
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Mmmm, I did a trip round the IOW which ranged from a pootle into Cowes and Yarmouth and some WOT messing about. Ive got twin 175's on the back and did about 1.4km per ltrs.

Did you leave the anchor down
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Old 26 August 2014, 09:58   #5
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On a more serious note - wouldnt the trim affect it a lot ?
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Old 26 August 2014, 10:32   #6
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What's your hull like. If it's bad dirty that'll cos extra burn


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Old 26 August 2014, 10:43   #7
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I have a 135 Mariner V6 on my 17ft hardboat, At 5500 rpm you can watch the petrol gauge move, when cruising at 3500 it lasts slightly longer....

I love the sound and acceleration but can do the tank (50 litres) in an afternoons skiing and general bobbing about. Did a 25 mile run from Carradale to Campbeltown and back one morning with the family and emptied the tank which also made me think 2 litres a mile at WOT !!

Had a 115 on it previously but lacked the grin factor! But fuel went further.....
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Old 26 August 2014, 11:01   #8
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have the carbs been serviced and set up correctly?
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Old 26 August 2014, 11:06   #9
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i sure am glad we use gallons over here. My 7m with a 250 does about 3mpg or 1.13L/mile!! at 36mph.
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Old 26 August 2014, 11:12   #10
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Quote:
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I have a 135 Mariner V6 on my 17ft hardboat, At 5500 rpm you can watch the petrol gauge move, when cruising at 3500 it lasts slightly longer....

I love the sound and acceleration but can do the tank (50 litres) in an afternoons skiing and general bobbing about. Did a 25 mile run from Carradale to Campbeltown and back one morning with the family and emptied the tank which also made me think 2 litres a mile at WOT !!

Had a 115 on it previously but lacked the grin factor! But fuel went further.....

At WOT I would expect it to probably do 2 lts per mile but on Sunday we were doing mid 20's if I went WOT I reckon I'd get 50kts as she does mid 40's with a lot more to go on the throttle.
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Old 26 August 2014, 11:17   #11
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What's your hull like. If it's bad dirty that'll cos extra burn


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Hull is shiny clean and kept on trailer out of the water

The dog modelling the hull while hiding in the shade
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Old 26 August 2014, 11:31   #12
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By simple maths I'd expect the fuel consumption to roughly half at half the revs. My outfit with nobody in it weighs in at @750 kilos so with my 18 stone plus the wife & three kids we're a fair weight.
Have you had it into a GOOD service establishment to have it looked over ?
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Old 26 August 2014, 11:39   #13
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Went in dave crawfords at lymington for a service but due to one of the voltage regulators bursting into flames it only got a fuel pump rebuild and regulators changed.
They said it looked so clean that they reckoned the carbs were nice and clean.

Keep meaning when I got out to put the quicksilver quikleen through it by adding to fuel but keep forgetting.
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Old 26 August 2014, 11:46   #14
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Quote:
Originally Posted by Solent Bombard View Post
Went in dave crawfords at lymington for a service but due to one of the voltage regulators bursting into flames it only got a fuel pump rebuild and regulators changed.
They said it looked so clean that they reckoned the carbs were nice and clean.

Keep meaning when I got out to put the quicksilver quikleen through it by adding to fuel but keep forgetting.
May "look clean" but have they been set up and balanced?

Compressions all even?
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Old 26 August 2014, 11:46   #15
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There'll be a way to make it run leaner by adjustment on the carbs but I've no idea how to advise you to do that.

Sorry.
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Old 26 August 2014, 12:38   #16
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Take the six drain drain screws out the bottom of the carbs one at a time and check that a main jet has not fallen out one of them. Punctured float? Dickie needle valve? Fuel pump diaphram?
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Old 26 August 2014, 13:01   #17
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Run loads of these lumps and there better than that normally

Check as Davies said,,
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Old 26 August 2014, 13:30   #18
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May "look clean" but have they been set up and balanced?

Compressions all even?

Compression on 6 cylinders were all around 120psi carbs look all to be running good but not had them cleaned thoroughly yet.

Here's a short video of the trip on Sunday I just video'ed the engine while running to check if the engine height was good it looks reasonable nice and clean out the back end

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Old 26 August 2014, 13:39   #19
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Had a few issues with mine until it took a battering on the beach which seemed to shake the crap about in the carbs and it flew afterwards and that has given me the excuse to clean them. I drained them initially & it didn't help.

Any good tips on how to make sure I do it right?

I hope this isn't a thread hijack...
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Old 26 August 2014, 14:17   #20
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Just watched a 3 part youtube of a guy stripping down V6 carbs. Is it necessary to do a complete strip or will removing the float bowl and giving it a good blow with the airline do ?
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