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Old 12 January 2009, 15:02   #1
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Petrol Outboards v's Diesel Inboard 8.5m Rib

Does anyone have any fuel consumption comparisons on single or twin outboards v's inboard diesel.

I am considering twin 150 or 225hp outboards (perhaps four stroke) v's a single diesel sterndrive on an 8.5 m rib.

The rib will be coded and used commercially, thereore I'd be in a position to claim the duty back on the fuel.

Any other thoughts would be appreciated.
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Old 12 January 2009, 15:13   #2
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8.5mtr approx 350hp diesel, 2800kg returns about 1 mile/litre. Approximately the same as a 6-6.5mtr rib with medium outboard.
I can't imagine a couple of 200hp petrols can get near that. However, performance will be different.

Availability of petrol and how much you enjoy carrying jerry cans may be more of an issue.
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Old 12 January 2009, 15:44   #3
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Do you run commercially? If so, what is your net diesel price /L currently?
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Old 12 January 2009, 16:08   #4
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Originally Posted by Ashton View Post
Do you run commercially?
Nope, I don't. Purchase price of diesel varies daily. For commercial use the duty is 10.07p and vat is 5%. Today it was 36p/lt +vat here. For leisure use it would be the 36p + 42.28 duty + Vat.
But, looking at your profile, I presume you know all this.
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Old 12 January 2009, 18:52   #5
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Outboard powered operators

Can any outboard powered operators shed some light on consumption an on fuel purchase? All help/advice welcome, however trivial you may consider it!!
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Old 13 January 2009, 05:36   #6
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Quote:
Originally Posted by jwalker View Post
8.5mtr approx 350hp diesel, 2800kg returns about 1 mile/litre. Approximately the same as a 6-6.5mtr rib with medium outboard.
I can't imagine a couple of 200hp petrols can get near that. However, performance will be different.

Availability of petrol and how much you enjoy carrying jerry cans may be more of an issue.

a mile a litre holy crap i dont get that out of the 5.4 with the yam 80.
i knew there was a reason i wanted a bigger boat with a nice turbo diesel V8. i could have a wheel house with a heater too...........
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Old 13 January 2009, 06:24   #7
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Originally Posted by doggypaddle View Post
... i could have a wheel house with a heater too...........
Of course you could!


And then you'd be able to buy some cheaper fuel too.
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Old 13 January 2009, 06:42   #8
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I also use less than 1 litre per mile. This is on an 8.75m with 315hp Yamaha inboard.
I take what JW says as accurate..........but aren't there other arguments if running commercially.
Specifically: availability, you can stop a fisherman miles offshore and ask for some fuel. You can also get it dockside in a very large number of places. I can remember getting some from a tiny, tiny fishdock inside Loch Roag once.
Also, maintainability. You can swap an outboard fast and get back to work v. quickly, especially if you had a spare engine. But the cost and survivabilty of outboards is as nothing compared to a diesel inboard.

All in all, you have got to take all factors into account and make your own decision............and having made it, live with it.
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Old 13 January 2009, 06:49   #9
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Was burning anywhere around .75-1.15 ltr per mile per engine with the 11m Redbay (twin Yamaha 245hp), With the 9.1m I was about .5 ltr per mile per engine (twin 165hp Yamahas).
It would really depend on what type of work I was going to do with the boat if I went for Inboard or outboard.
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Old 13 January 2009, 07:58   #10
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roughly speaking it's probaly about 4 time dearer in fuel terms to run a petrol outboard than the same hp diesel inboard, the v8 yamaha 350hp burns 27gals an hour flat out and you can see from the other posts that aint the case with diesel, you could argue the toss for ever with people saying things like maintainance, power to weight, cost of purchase, installation, space in boat etc, i could go on, but the bottom line is in my own view diesel boats win hands down, i'm not getting into arguments as i have with certain people on this site about this subject, i worked in the rib industry more or less ever since ribs started and have been in countless boats doing sea trials, round britian, deliveries etc and my advice to you is if you can afford a diesel 8.5 buy it. posted a few pics of some bits that might be of interest, my yellow boat burns about 17lts per hour at 42 knots (its roughly that, i dont keep tabs on it a lot) and i've never broken down, it's never failed to start, all i've ever done is change oil, filters, two belts and one impellor in 900hours
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