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  1. #1
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    Apr 2005
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    Default 45ft ish catamaran owners: a question about fuel consumption

    Can I ask anyone with a reasonably recent mid 40s cat some questions about motoring:

    Is it possible to comfortably motor at Hull speed or just above (7-8knts)
    Do you tend to motor on one engine or does the turning force mean it’s better to use 2?
    What sort or fuel burn do you see at a decent speed (7-8knts)
    What sort of size fuel tanks do most cars this size have

    Thanks in advance
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  2. #2
    Join Date
    Nov 2009
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    Home UK Midlands / Boat Croatia
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    18,609

    Default Re: 45ft ish catamaran owners: a question about fuel consumption

    My 40 footer will do 7 knots but I wouldn't say that it's comfortable as that's around 3000 rpm which is well above what I cruise at. I would guess that a 45 footer will be a lot more relaxed at 7 but I think 8 will still be quite boisterous.

    I don't usually motor on one engine although I have done so when I've had a technical problem. I can't say that either I, or the autopilot, notice any difference except that it's slower.

    I haven't really checked fuel but it seems to be economical. I've got two 175 litre diesel tanks.

    Richard

  3. #3
    Join Date
    May 2003
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    Eastern Atlantic seaboard
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    2,990

    Default Re: 45ft ish catamaran owners: a question about fuel consumption

    Crossed the pond last year on a 50' Lagoon with 2 x 80hp Yanmars. There was a marginal advantage in fuel economy running one engine to maintain 5.5 knts, burning 6l/hr.
    During the run-in from Bordeaux to Cascais using max revs a lot we burnt up to 16l/hr giving 8.5knts through the water. Ouch! A 4 figure fuel bill for a 600 mile trip. How I pity moboers.
    Last edited by Quiddle; 12-04-19 at 17:41.
    I'd rather be tethered to a pad eye than tethered to an iPad.

  4. #4
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    Apr 2005
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    Default Re: 45ft ish catamaran owners: a question about fuel consumption

    Ok thanks.

    Do sensible cruising speed should be more 6-6.5knts from a fuel burn POV.
    80Hp motifs sounds sporting - I think the upgrade for one of the cats I’m idly considering is 57Hp, standard I think is 40-45Hp

    In my current 50ft boat at 8 knots we burn about 32l/hr. let’s not discuss 20knts....
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  5. #5
    Join Date
    Jan 2004
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    Med
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    5,676

    Default Re: 45ft ish catamaran owners: a question about fuel consumption

    Quote Originally Posted by Whitelighter View Post
    Ok thanks.

    Do sensible cruising speed should be more 6-6.5knts from a fuel burn POV.
    80Hp motifs sounds sporting - I think the upgrade for one of the cats I’m idly considering is 57Hp, standard I think is 40-45Hp

    In my current 50ft boat at 8 knots we burn about 32l/hr. let’s not discuss 20knts....
    32 LPH ?? , am I reading that right ?
    Warning forumite dyslexia near by
    www.bluewatersailorcroatia.webs.com

  6. #6
    Join Date
    Dec 2010
    Location
    South Oxfordshire, Gosport and Wellington New Zealand.
    Posts
    7,748

    Default Re: 45ft ish catamaran owners: a question about fuel consumption

    We have a single 110 HP Turbo Yanmar in our 12.5 metre motorsailer.

    Over the last 4,000 NM we have averaged just under 4 LPR. Usually with some assistance from the sails.

    2,200 RPM-my prefered cruising RPM if the wind will not serve- 3.2 LPH.

    But, thread drift, as not a 45 foot cat................................

  7. #7
    Join Date
    Feb 2017
    Location
    Türkiye
    Posts
    1,493

    Default Re: 45ft ish catamaran owners: a question about fuel consumption

    More drift but my 10.3M motor cat has 2 x 75HP Yanmars. I motor almost exclusively on one engine doing 7 Knts @ 2200 rpm and burning 3.5 lph. If I employ both engines @ 2200 she makes 8.5 Knts for double the fuel burn.
    Last edited by Irish Rover; 14-04-19 at 07:27.

  8. #8
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    Apr 2005
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    Default Re: 45ft ish catamaran owners: a question about fuel consumption

    Quote Originally Posted by sailaboutvic View Post
    32 LPH ?? , am I reading that right ?
    Yes. You are reading that correctly
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  9. #9
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    Apr 2005
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    Default Re: 45ft ish catamaran owners: a question about fuel consumption

    Quote Originally Posted by Irish Rover View Post
    More drift but my 10.3M motor car has 2 x 75HP Yanmars. I motor almost exclusively on one engine doing 7 Knts @ 2200 rpm and burning 3.5 lph. If I employ both engines @ 2200 she makes 8.5 Knts for double the fuel burn.
    Well not total thread drift. Still useful info thanks
    Free supercharging Tesla referral code http://ts.la/jez9763

  10. #10
    Join Date
    Jul 2009
    Location
    Winter in Falmouth, summer on board Rampage.
    Posts
    5,032

    Default Re: 45ft ish catamaran owners: a question about fuel consumption

    I moved a 42 foot Fontain Pajiot cat from Lefkas to Barbados winter before last. When motoring it was normally at about 6.5 knots on two 30 hp engines running at 2200 rpm: that burnt about 4-4.5 lph. As above, running on one engine meant running it at about 2600-2800 rpm with a boat speed of 5.5 knots: no noticeable handling problems (did a fair bit of one engines running as we had diesel bug problems that often knocked out an engine....).
    The cat had a 600 litre diesel tank. I also carried 200 litres in jerrycans on the leg from Tenerife to Barbados: didn’t actually need them as we arrived with 300 litres left.

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