How accurate are the Fuel Flow meters
 

I have an evinrude e-tec 250 connected to a Ballistic 7.8. Whilst out today I noted that at 4000 rpm the fuel flow meter was reading 50 l/h and at 5000 rpm it was reading 72 l/h. These values seem extreemly high. The figures quoted in the Rib Magazine review of the engine attached to the same boat quote 24 l/h and 36 l/h respectivley.

My question is, is my fuel flow meter giving dodgy readings or is the engine burning to much. Can anyone else with a simular setup comment on these figures.

Thanks

Neil

what speed were you traveling at?

Today I was travelling at around 40mph at 4000rpm and 48mph at 5000rpm taken from the GPS.

Engine maxs out at just over 5000rpm

By my calcs then you were running at 1.4 litres per nm and then 1.7 litres per nm. Maybe not the best figures in the world but not massivley out either I dont think. My Opti 225 used to return around 1.3 and 1.5 l/nm at similiar speeds and my Verado 275 is obviously a little higher so I think it sounds about right...

You know, you have to calibrate the fuel meter? The more often you do that, the better the results.

I have an Evinrude 250 DI 2004 with 60km/hr and 40 lt/hr at 4000 r/m and
80km/hr, 58 lt/hr at 5000 r/m.
At 5900 r/m 98 km/hr and 94 lt/hr.

The figures from the artical ribmagazine.com big guns shootout are:

RPM FUEL CONSUMPTION
2,000 6 litres per hour
3,000 12 litres per hour
4,000 24 litres per hour
5,000 36 litres per hour

My reading are far from this.

I find those very hard to believe, it would put you under a litre per mile and for a 250 hp engine thats pretty amazing. Wonder how they made that calculation?

The artical quotes the following:

YAMAHA F250 V6
RPM FUEL CONSUMPTION
2,000 6 litres per hour
3,000 12 litres per hour
4,000 21 litres per hour
5,000 48 litres per hour

MERCURY VERADO 250
RPM FUEL CONSUMPTION
2,000 6 litres per hour
3,000 9 litres per hour
4,000 21 litres per hour
5,000 72 litres per hour

SUZUKI V6 250
2,000 3 litres per hour
3,000 9 litres per hour
4,000 18 litres per hour
5,000 44 litres per hour

EVINRUDE E-TEC 250
2,000 6 litres per hour
3,000 12 litres per hour
4,000 24 litres per hour
5,000 36 litres per hour

They do seem very low figures for the size of engines.

Neil

If those figures are correct how glad am I that I have gone for Suzuki!!:thumbs:

All the best

I think you will find there was a "degree of controversy" over the RIBinternational article in the first place - https://www.rib.net/forum/f36/engine-tests-rivas-ballistics-12623.html

There is an old "rule of thumb" that each 10HP required 1 US gal per hour at full throttle in "traditional 2 strokes". Thats about 96 L/h for a 250 HP. 4-strokes apparently use about 25% less. And the DI 2-strokes are usually claimed to have similar efficiency to a 4-stroke ... so at FULL throttle I would expect a 250 HP Etec to burn around 70 L/h.

My 150hp Opti burns 60l/hr at WOT according to the Smartcraft gauge.

It's reasonably accurate as what we put in after each trip is within a few litres of what the gauge claims has been burnt.

Suzuki 300
 

My Suzuki 300, at 5400rpm (WOT 6300) but on over pitched prop (1.5in) 49knts on a RIBCRAFT 7.8 with 2 crew and full fuel load is burnig 84Lh very slight sea state.
Dissapoiting that the new fly by wire system and all digi readouts dosn't have a facility to display a average burn rate over a specific transit / leg. Or perhaps it does and I just hav't read the instruction booklet properly.
:]

We run twin 200 ETECs on our Humbers. At 4000rpm we are cruising at about 30 knots and burning 43 litres/hour/engine. RPMs and speeds will of course depend on prop size, sea conditions and boat loading, but I reckon that your figures sound reasonably accurate.

Does seem a little high....just been out this week end running etec 225 ho on 8mt ribs getting 35lts-40lts @4000 rpm, choppy water/24pich prop
Our 6.7mtr rib with a 175 etec done 126lts over 137miles..... have you set your calibration on the guage....

Engine maxs out at just over 5000rpm [/QUOTE]


Your fuel figures sound a little High , But from the sounds of it your over proped , and this could account for you higher fuel burn

The Rib magazine, are unrealistic...... and you might get 10% better if you have the boat set up and trimmed right.

drivers and trim make a diffrance ?