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Old 30 August 2014, 17:50   #31
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Carb overhauls

2L/nm doesn't seem massively over what you might expect if you're driving it hard but still amounts to scary fuel bills. For ref I've now got a 150HPDI which does around 1L/nm even driven hard but I recon my old carb'd mariner 75 drank twice that.

I'd still be checking everything out - worth it given the cost of fuel. As posts above, do check trim / prop / engine height etc, but I'd definitely be checking the fuel system over. Dropping the float bowls off might uncover a significant problem (holed / stuck float, missing main jet), so definitely worth doing, but won't uncover more subtle tuning issues. Checking your plugs will also tell you if you've got a cylinder running 'off' - try to do this as soon as pos after a flat out blast - lots of idling will tend to oil the plugs and cover the problem.

Don't however try to tune it yourself unless you know exactly what you're doing and have the kit to balance a 6-carb engine - you'll almost certainly make it worse. Definitely don't lean-off the mixture to try to save fuel - unless you get it right you'll end up with holed pistons.

Ignition timing will also affect fuel consumption and is easy to check if you've got access to a strobe light.
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Old 05 September 2014, 02:35   #32
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Country: UK - England
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to make you feel better..

I went from Cowes to Weymouth on Wednesday back yesterday. Used 150 each way...135 Optimax, 5.85 Vipermax. Couple of mates did the same trip as well 135 Optimax and 6m Avon, 90 each way..
Jim
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Old 05 September 2014, 03:34   #33
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I went from Cowes to Weymouth on Wednesday back yesterday. Used 150 each way...135 Optimax, 5.85 Vipermax. Couple of mates did the same trip as well 135 Optimax and 6m Avon, 90 each way..
Jim
Cowes to Weymouth is about 55Nautical Miles .... so thats about 2 litres per NM which is really bad.

Our 7 Meter Vipermax with a 250 on the back would do that trip and use half the fuel....
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Old 05 September 2014, 03:43   #34
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There seems to be a direct link between helming style and fuel consumption with the bigger engines.
If I have the family in my 135 V6 Mariner drinks roughly half the fuel in spite of the extra weight that it does when it's just me

If it's flat calm you're going to go a lot further/faster than when it's rough so this too has a direct link.
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Old 06 September 2014, 16:34   #35
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What speed does your boat start planing at?

How far did you go at sub planing speeds as this can make a huge difference if you came out of the harbour off the plane for some distance.


Have these got six carbs? as I've done triples many times over, they are easy to sort out & balance, buy yourself the kit to do it properly & its easy enough diy if you read up.
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Old 07 September 2014, 07:42   #36
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Well after Friday evening the fuel issue is no longer a problem with this engine.

5 mins into a trip on Friday evening the No6 piston let go started smashing into the cylinder head and has given the cylinder block a good going over as well.




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Old 07 September 2014, 07:55   #37
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Old 07 September 2014, 08:33   #38
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Well after Friday evening the fuel issue is no longer a problem with this engine.

5 mins into a trip on Friday evening the No6 piston let go started smashing into the cylinder head and has given the cylinder block a good going over as well.





Bloody oil pumps. What os your plans now with this engine
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Old 07 September 2014, 08:51   #39
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Sorry was on phone

Are you going to rebuild it ?

Got lots of bits for these lumps dependant on year
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Old 07 September 2014, 10:27   #40
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Well it's a 1999 v6 carb model. (Pre optimax)

And looking at the damage I would need

Cylinder block I guess with heads (if it's the same as motorbikes there mated so need both)

Pistons (might as well change them all)

And I would expect Conrod minimum maybe even whole crank depending on the hammering it's took.

And other stuff I guess but have not took too much apart yet just took the head off to asses damage.

Bloody pissed me off because the last couple of months I have sunk over 1500 into that engine.

Gearbox refurb, New water pump parts, updated voltage regulators etc etc including a service as well.

Bloody typical.
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