LPH Ribeye 6m F115

Plankton21 · 28 April 2019, 18:19

I’m taking delivery of my New (second hand) Ribeye 6m at the weekend. My previous boat GRP 18’ Fletcher had a 2 Stoke 115 Mercury used to drink fuel, so looking forward to some range and not spending £100 every couple of days while boating. A friend has a 6m Cobra with the same engine (5 year old Yamaha F115) and thinks he uses 13 Litres per hour at 20 odds kts cruising on calm water. Does this sound about right (assuming nice clean bottom, trimmed right and a couple of people on board) ?

Orwell boy · 28 April 2019, 19:39

i have a 115 on my nautica 19 ,easily get 1mile per litre , if you think about it it makes far more sense , if you get about at 60mph for 1 hour yuo will hav burnt 60 litres and travelled 60 miles ,if you travel at 20 mph for 1 hour you will travel 20 miles and burnt 20 lires .....this is not scientific ,just an approximation

lakelandterrier · 28 April 2019, 21:57

Sorry, disagree with OrwellBoy.
Fuel consumption is not straight line - faster you go the more fuel burnt per NM.

Fuel used will depend on speed / revs. If I with 140HP 4-stroke on a 5.85m cruise @ 4000 rpm (c. 22kts) I'll get 0.75l / NM if calm. If I up to 28kt @ c4800-5000rpm I'll drop to 0.85-0.9l /NM

I'd have thought on the Ribeye setup with a 115 you should get well under 1l. / NM @ 22-25kts. A few run if you note NM travelled & fuel replened to top the tank up will give you a working usage for the ribbing you do.

Plankton21 · 28 April 2019, 22:09

Thanks for the replies. Yes my plan is to do some maths to work out some accurate consumption figures, always good for journey planning. I think a working assumption of a litre per NM at crusing speed of 20 knots or so will serve me well till I’ve got my own figures ...

Lee argyle · 28 April 2019, 22:21

Quote:

Originally Posted by lakelandterrier

Sorry, disagree with OrwellBoy.
Fuel consumption is not straight line - faster you go the more fuel burnt per NM.

+1

A lot of outboards roughly double their fuel usage every thousand revs, the bigger the grin the less money for ice cream for the kids! Lol

Orwell boy · 28 April 2019, 22:43

+2.......
sorry it was,nt a statement about accuracy ,and your right it does,nt remotely suggest a comfortable cruising speed will return a bettter mpg than roaring about ,which is of course fairly obvious ,it does,nt refer to the possibilities of a following sea or the wind in your face either . sorry it was a loose non scientific post ,mainly trying not too write reems ,which i know have too, to avoid being seen as a idiot .....sorry

Fender · 29 April 2019, 09:27

Mercury efi 25 - 40 - 50 - 75 - 90 - 115 - 150 - 175 - 200 - 225 - 250 - 350 hp SCi Verado Outboard Fuel Consumption Liters per hour | Portable 3.5 - 4 - 6 - 8 - 9.9 - 15 hp

Plankton21 · 29 April 2019, 10:28

Fender thanks, I've looked at this figures before, they give voted estimates at WOT (Wide open throttle) for the F115 this is 36 LPH, which I think is going to be about right. What I'm after is the LPH at plaining cruise c 21knots in a flat sea for this set up Ribeye A600 and F115. I've obviously figure it out when I get hold of the boat, just trying to estimate a working assumption for initial passage planning. I think I'm going to be looking at around 14 LPH or 0.7 litres per NM, but am going to work on 1 litre a NM calm/ 1.5 litres a NM for choppy.

lakelandterrier · 29 April 2019, 11:30

I've never found for the coastal journeys of 30-120 NM I do, LPH to be a useful measure as I will vary speed - I find Litres / NM a better planning / working figure.

I've just worked it out - I average, c.10.7LPH but don't plan engine hours on a run.

When is LPH a better metric then L/NM?

paulbrown22 · 29 April 2019, 19:19

On our old Avon Adventure 620 with a Yam 115 4-stroke we had a fuel flow gauge, and that showed pretty much 1 litre/hour/knot in flat conditions.

So straight cruising at 15 knots was consuming 15l/hour, cruising at 30 knots was 30l/hour, etc. If you're using power on/off in tough conditions, obviously that will go up.

Orwell boy · 29 April 2019, 21:17

Quote:

Originally Posted by paulbrown22

On our old Avon Adventure 620 with a Yam 115 4-stroke we had a fuel flow gauge, and that showed pretty much 1 litre/hour/knot in flat conditions.

So straight cruising at 15 knots was consuming 15l/hour, cruising at 30 knots was 30l/hour, etc. If you're using power on/off in tough conditions, obviously that will go up.

i too have the speed and fuel yam gauge on my 115 (it is a second 4" ish lcd gauge similar to the Tach gauge ,but has speed and fuel written on it ) ,i find the most useful feature is to reset the gauge before leaving port and you have a running record of fuel used ,with mine the miles covered is always well ahead of the litres burned

Plankton21 · 29 April 2019, 21:22

Paul thanks. Lakelandterrier ... For me if I’m going from A to B I’ll be thinking LPNM, I do a lot of diving and this is what we work with on our club ribs for planning. If I’m water skiing and doughnutting then I’m going to be thinking LPH. Obviously the maths are inter changeable. But taking Paul’s example. 15lt per hour at 15 knots is 1 litre per NM .. his 30lts per hour figure for 30knots would make me want to be sure that I’d got 60 litres plus enough to get home if the plan was an afternoons waterskiing etc ....

lakelandterrier · 29 April 2019, 21:45

I fully agree with knowing L/NM for the types of ribbing / conditions.
I also work on keeping a 30% reserve (or carrying extra fuel to ensure this).

Were I water skiing or doing something similar I'd still know that for that activity I went X far and used Y fuel so it would come back to L/NM for that activity / condition. I'm not sure how L/NM is a valuable metric, as it will all depend on rpm which will change over a passage / activity.

gpsguru · 29 April 2019, 21:59

I use the same 'old skool' fuel method as LT...... a third to get there, a third to come home, and a third in reserve .......... that gives you the option of dropping to displacement speed and still having enough fuel to get back.

This might help a bit ....... real time figures for a DF140 on a 585

585Df140-Performance.pdf

lakelandterrier · 30 April 2019, 18:16

Quote:

Originally Posted by gpsguru

I
This might help a bit ....... real time figures for a DF140 on a 585
Attachment 129198

Wish I got 30+kts @4,500rpm from my 585 and DF140!

The 4,000rpm figure is bang on.
4500rpm gives me only c. 25-26kts but will deliver the stated 0.84 L/Nm.

kerfoo · 30 April 2019, 19:23

This is my go to consumption graph for my 115 (link below). Units are wrong but you get the idea. Most efficient RPM is 3500 but you don't lose much efficiency up to 4500. After that you're burning $.

If you do the conversion, 6.13 mpg comes out to 0.71 l/nm so slightly better than the DF140 test at 0.75 which makes sense. So optimum cruise on the test boat is 18.4 nm/hr at which point you'd get 13.08 litre/hour. A 6m Scorpion at 20 knots and burning 13 litre/hour is really efficient at 0.65 litre/nm. (I may have messed up some of the conversions above but they're in the ballpark)

I have a Highfield 590 with an F115 and get about 18.5knots at 3500RPM fully loaded - similar to the Zodiac tested although I think I'm ligher.

kerfoo · 30 April 2019, 19:24

http://yamahaoutboards.com/en-us/hom...-18-2018-1_inf

gpsguru · 30 April 2019, 20:42

Quote:

Originally Posted by lakelandterrier

Wish I got 30+kts @4,500rpm from my 585 and DF140!

The 4,000rpm figure is bang on.
4500rpm gives me only c. 25-26kts but will deliver the stated 0.84 L/Nm.

How does your weight compare to the test boat ?

They are estimating my 'dry' weight to be 982kg (ish) ............

lakelandterrier · 30 April 2019, 21:25

Quote:

Originally Posted by gpsguru

How does your weight compare to the test boat ?

They are estimating my 'dry' weight to be 982kg (ish) ............

I have:
Pacific console
4 x single jockey
Single battery
90l tank
A-frame
decent anchor, 8m, chain 80m+ heavy anchor line
Guess v. similar to your set up
Self and regular crew probably weigh in @ 190kg ish between us (sorry Mark!).
I reckon boat is c.1 tonne before crew clamber on.

to be fair the RC stats may be light crew, ideal conditions, light on fuel / kit, optimal prop, but then I'd expect even better figure @ 4000 rpm 20kts.

That said, it's still efficient and relatively light on wallet compared to many boats, so i'm not really bothered

When do you pick her up?

Plankton21 · 30 April 2019, 21:38

Picking the boat up from Saltash, Friday morning, then haul to Brighton then in the water Saturday morning into Brighton Marina. It’s going to go back to South Cornwall for July and August for it’s summer holiday. Just got to navigate the M25, which will be the most treacherous journey the boat will make this year.