Fuel Consumption
Submitted by Bodie on Thu, 2009-04-16 15:31
Hi All
Curious to know what people are getting for Economy on different boats and engines.
i have a 3.5 tonne 26 foot Fibre Centre console
Twin 140hp Bombardier Johnson 4stks.
Currently running at about 2-2.25 ltrs per Nuatical mile.
I thought this seemed quite high??
Just had a mechanic come look at my engines for another issue, and he said he had just fitted a 300hp Suziki 4stk to a 3.5 tonna glass boat, and at cruising speed its using 1lt per 1.1 nautical miles!!! bloody good!
Whats everyone elses economy like?
Blank Cheque
Posts: 221
Date Joined: 28/03/09
Have a look down the page
Have a look down the page a bit, heading Blank Cheque new member. A couple spaces down i reply giving a run down on mine. Same weight boat running Twin 200 EFI MAriners.
Its a bit late to head home early.
Its a little late to head home early
Simon C
Posts: 801
Date Joined: 01/05/07
I think the issue with fuel
I think the issue with fuel consumption is everyone has a different expectation of "cruising speed". I can probably get around the 1nautical mile per litre on a 150 etec if I want to sit at 15-16knots on a flat day - but why the hell bother when I can sit on 25-28 knots and drop to .nm per lt. Only time it bothers me is when I am low on fuel, and that has only happened once.
Twins also use a lot more fuel on a single hull because of the extra leg drag so I recon you probably are not to far of the money, you may well see a reduction by running a big four stroke single.
Blank Cheque
Posts: 221
Date Joined: 28/03/09
I think you
Hit the nail on the head Simon. Whats cruising speed in my boat may not be cruising speed in yours. All boat have a happy medium speed I know if mine is sitting on 3000rpm its on the plane but still labouring. The list goes on Prop size prop pitch max RPM etc.
You are getting about the same as mine looking back. I am running 2 strokes and your running 4 stroke.
Another guy i spoke with once from NOR had lesuire cat behind a Dina truck. Same size boat as mine. He was running 2 x 250 4 St Yamaha and saving 20 lts of fuel compared to mine over the same distance.
Its a bit late to head home early.
Its a little late to head home early
Bodie
Posts: 3758
Date Joined: 05/11/07
More interested in finding
More interested in finding out differences between how and weight, and engine types against weight.
Most cruising speeds should be similar i would ahve thought for relative boats.
Decella
Posts: 401
Date Joined: 01/02/09
Wieght=prop size
I have a 175hp E-tec on a reef runner appr. 2.5 tonne. I do 1nm per ltr no matter what i'm doing, but I only carry one other person and what i need when going fishing. One of my mates changes his prop dependant on the amount of people and gear he is carrying. If your boat is labouring when it is trying to fight the swell then you need to reduce your pitch so that you will get a more even "push" instead of it bogging down and using more fuel to get back to your desired RPM.
Hope this helps.
Rick
Posts: 1104
Date Joined: 22/12/06
Mercruiser
OK not apples with apples, but Leeder Tomcat 7.4m glass boat loaded with fuel and gear for 2 adults weight is around 2.8t.Powered by 4.3 MPI at 220HP
Did a trip a few weeks ago on one of those glass off days. We covered 95.4NM for the day. Logged from the GPS, and I would say over 70miles of that was with the motor at 4000rpm or better.
Fueled up the following day and it took 201 litres.
So just a fraction over 2 litres per Nautical Mile.
Normally run around 3600 to3800 rpm as good cruising speed.
PGFC Member
HuggyB
Posts: 2515
Date Joined: 03/08/08
single v twins
in your comparo to the 300hp boat, a few things to consider are:
1. you have at least 100kg weight difference in motors, possibly more.
2. you have two legs = more drag in the water to overcome.
3. you are conceeding +20hp
4. you are comparing a high capcicty V6 engine against your 2 x smaller capacity 4cyl engines - the torque difference alone would be a factor. more torque = less power req to spin the prop.
5. not all 3.5T hulls are the same! Sounds obvious, but to get a real reflection you would have to compare apples with apples. Comparing your Fury to a Leisure Cat or a Boston Whaler or a Bayliner is pointless exercise IMO - they are all different hulls that plane differently, shaped differently etc etc.
The Terrorist - coming to a fishing spot near you.........
Frank F
Posts: 481
Date Joined: 17/03/09
7m Leisure cat 140 suzuki
I have a 7m Leisure cat with twin 140 suzukis it weights about 2.8 t and on a
reasonbly good day I cruise on at 5000 rpm which the speed is 24-26 knots and the
fuel consumption is around 1-1.2 littres per nautical mile.
sunshine
Posts: 2555
Date Joined: 03/03/09
Fuel consumption
Well I run a 6.8 Seaquest Ali with an old 200hp Johnson and a 4 blade ss prop from Just Propellors.
It is a jointly owned boat which is why I have posted. When I skipper the fuel consumption is almost twice as good as when skippered by the co-owner but I spend time carefully trimming out the motor until you cannot hear any form of surging (as in when you dig into a wave through trimming too steeply). I also avoid trimming too high and banging the boat as my old neck wont take it.
Fuel consumption seldom exceeds 1.35 litres per nm and that is up to and including speeds of 30+ knots in good conditions
My old 18 foot glass boat had a 90hp Etec - amazing fuel economy - used to run on the smell of an oily rag doubling the economy of the 70hp model it replaced. Would like to repower the current boat and probably would have done but for getting my marching orders from work after 17 years.
In my view the prop is critical - if in doubt go and see Michael in Ossy Park and seek some advice
Paul G
Posts: 5215
Date Joined: 12/12/07
Last trip to the bank from
Last trip to the bank from Two Rocks and back plus running between patches ,60mile i would guess used 50-60 litres fitch 175 evenrude-635 haines sitting on around 3800 rpm 22knots not bad for a two stroke..on a big day out i would use 100-110 litres for a 80-90 mile trip speed from 22-28 knots..
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Bodie
Posts: 3758
Date Joined: 05/11/07
Im only calculating my fuel
Im only calculating my fuel consumption off the GPS from my last 2 trips, but i will fill it up tonight and should get a more accurate reading.
Im not real sure what labouring is?? is this when you ride swell and it bottoms out??
Not very often boats with twin screws does this... more pushing power with twin screws.
Maybe my driving on the last 2 trips wasnt as 'economical' as it could have been :\ , did have to pump out 22 mile into a 15-20knot easterlie in a 2m swell so may not have helped.
Wazo
Posts: 84
Date Joined: 12/06/08
300 etec
flat out everywhere, same distances as paul. prob drink about 150 to 175 litres per trip