Yamaha Fuel Consumption

CSR · 15 October 2011, 11:47

Hi folks. Ive got a Yamaha ME420sti in my rib and was just wondering if anyone knew roughly what the fuel consumption of this engine is? I know there are lots of factors which determine this eg boat size/weight, rpm’s, prop size etc etc but if anyone has a rough guide to this, that would be brilliant.
Thanks in advance

Portnahaven · 15 October 2011, 13:17

Hi CSR
Have just bought new 7.5 cabin redbay stormforce with the same engine with TRP leg.
All up weight must be near 2500kg as my fuel tank is 315lt with 65lt. wing tank, and aux outboard.
I have only put through one tank full of fuel so my calculations may not be too accurate yet - which is 17.5l/hour.
I think the props are 24" from memory. Will check that tomorrow and let you know if that is incorrect.
Hope this is some help.

willk · 15 October 2011, 13:35

Wing tank, eh? Where did they fit that?

CSR · 15 October 2011, 14:07

Hi Portnahaven.
Crikey a 315L tank? I think mine has a 150L or a 180L tank depending on what you pay attention to. The salesmen at Redbay or the sticky label on my dashboard!! The sticker also says it will do 10L/ph but im not sure at what rpm this is or if its even true. Id be quite intrested to see pictures of your rib if you wouldnt mind sending some to me? If you PM me ill pass my email address.
Thanks for your reply.

Portnahaven · 15 October 2011, 14:23

Looking down on the engine from cabin - square tank far left hand side , level with the top of engine. A bit of a squeeze.
Photo shows yellow strip on lhs where the wing tank is attached on.

Portnahaven · 15 October 2011, 14:35

I wanted a big fuel tank with reserve tank to give me plenty of range, even though it means lugging nearly 400kg extra weight.
As i say, being first tank of fuel my figures might not be accurate. Average speed on log is 18knts. Still running in engine, although it has been bliped up to 35knts.
PM`ing photos now.

Portnahaven · 15 October 2011, 14:56

Some photos-

CSR · 15 October 2011, 15:24

Wa wa wee wa. Very nice indeed. Thanks for sending these over. Good bit more modern than mine but if shes as sea worthy as mine you'll have no worries.

Portnahaven · 15 October 2011, 15:29

Many thanks-
Will give you a shout when i`m down your way

CSR · 15 October 2011, 15:31

Please do. Cheers.

willk · 15 October 2011, 16:24

I do like that boat. I bet the gelcoating team were cursing you

You've thought about your "brightwork" a lot - nice wraparound handrail there. Is that Craighouse pontoon? I have unhappy memories of that....

I had guessed that you should get about 1L/Nm from those engines, if they weren't pushed over 3000rpm.

jambo · 15 October 2011, 16:56

Is that Craighouse pontoon? I have unhappy memories of that....

It looks awfully familar to me too! But I have better memories of it than you

I can taste the 'Jura' from here

B

CSR · 15 October 2011, 18:21

Cheers Willk. I was running it at 3000 rpm since I got it but of late ive been trying to keep it at 25kts which is just about 26/2700 depending on the weather and how well its trimmed. Ive got a job on tomorrow morning so ill log the details of my trip and see if I can start working it out from that. (I should have been doing this from the start - I know!)

Portnahaven · 15 October 2011, 19:16

[QUOTE=willk;425491]I do like that boat. I bet the gelcoating team were cursing you

Maybe just a bit, more so with the glassfibre hardnose matched grey with the tubes. But they did a great job, and with the steelwork.
Yes Craighouse - our first trip after previous weeks launch. Glorious day - wind force 1-2, flat calm sea, sun shone all day (maybe it was all just a dream). Bit lumpier on return past Rathlin Is. to Fair Head with tide against us.

We are getting about 21/22 knots at those revs.

CSR · 15 October 2011, 19:21

Pretty much the same as mine then but you have slightly more weight with the fuel you carry so its probably pretty even. Keep me posted about your consumption with the new vessel. Ive made up a spreadsheet so ill keep a note of mine and try to work it out.

Portnahaven · 15 October 2011, 19:43

I`m doing the same, only in a little black book. When i run out this tankfull, will give me a better picture. First tank we were doing engine trials and prop changes etc - so hopefully get better results.

Searider · 16 October 2011, 13:41

As a rule of thumb 5 gallons per hour per 100hp used.

So, flat out, irrespective of speed, a 240hp diesel will use 12 gallons per hour.

Back off a little and this will halve.

Hope this helps as a starting point.

It's tricky just dividing fuel put in the tank by hours on the clock - you'd be surprised how much time is spent warming up / idling / pooling down the river on tickover etc and not at cruising speed.

willk · 16 October 2011, 13:48

Quote:

Originally Posted by Searider

It's tricky just dividing fuel put in the tank by hours on the clock - you'd be surprised how much time is spent warming up / idling / pooling down the river on tickover etc and not at cruising speed.

This is why I prefer L/Nm at "cruising" speeds. I find it more useful for passage planning, etc.

Portnahaven · 16 October 2011, 20:19

Quote:

Originally Posted by willk

This is why I prefer L/Nm at "cruising" speeds. I find it more useful for passage planning, etc.

Just worked out mine as 2.0 L/Nm - does that sound sensible?

willk · 16 October 2011, 20:22

Quote:

Originally Posted by Portnahaven

Just worked out mine as 2.0 L/Nm - does that sound sensible?

Not if you're running the engine in as mentioned... I think your pencil slipped!