Outboard Fuel Testing

[seamaid]

:D G/DAY
Perusing previous post, boaties have indicated fuel economy, being inquisitiveness, how are you achieving your results.
We all know several factors apply. eg.
Boat & motor weight,propping,persons on board,conditions on the day etc, etc.
Testing a 4.5 Quintrex, powered by a 60hp 2 stroke ( e- tec ) using seperate outboard tanks 5 liters capacity connected to the CAV fuel filter.
Boat/ motor weight all up with 2 persons aboard is 800kg.
Using GPS to measure distance.
Prop ( 1 ) 137/8 x 16p SST ----- 1.2nm per litre
Prop ( 2 ) 137/8 x 15p Viper --- 1.5nm per litre .
Previous attempts, Fill tank full, use fuel on trip of the day refill tank full, GPS gives distance, approx same results.
ALL Inboards, 4strokes & 2strokes comments.
PLEASE --- NO E-TECS VERSES OTHER, I AM ONLY INTERESTED IN THE METHORD OF TESTING.
CHEERS GED.

[FNQCairns]

Looks good! best way to do it also, some of the fuel figures expressed on here are a little confusing, refilling at different pumps, fuel stations with slants in their slabs etc make it hard to base reliable figures. So does figures that have lots of trolling in them, best to do the test at midrange cruiseing speed IMO everything else is just fluffs the result.

One thing for sure the 16p (in that diameter) was too big for your combo.

You could run a 16p just go down in diameter, it's large for your boat, would suit a 17ft fglass.

Lots of extra speed, extra fuel econ, range and a better boat overall if you go further.

cheers fnq

[Noelm]

never been too sure how relevant the litres per klm is, I think a litres per hour is a more constant reference to fuel use in a Boat, but it is harder to really measure, unless you do something like a set amount of fuel and a timer and see how long it goes for, or maybe fill up, use for a full day or timed period, on differing throttle use and then refill again, but to each their own, if litres per klm is your thing, then so be it, I guess it is better than nothing, I just think there is too many variables in a set amount of klms, like it could be as rough as, and you take 3 hours to go 1K but use 6 litres of fuel.

[Crocodile]

Google yamaha outboards performance bulletins.
There is a USA and an Australian page.
I think that it is safe to assume that these figures are based on careful measurements.
Seamedia has the best selection of Australian tests.
Boatpoint.com.au has engine reviews, showing usage at idle, cruise(4000-4500rpm) and wide open throttle.
The end result is that there is very little difference between brands.
Another pattern to emerge is that carb two strokes produce 10hp per gallon(4.55 litres) of fuel per hour.
A typical outboard running at 4000rpm is producing about half of its maximum power and using half of the fuel.
My 60hp Yamaha 2 stroke seems to support this, using about three gallons(13.5 litres) per hour at 4000 rpm, by inspection of the tote tank.
A typical 4 stroke produces 12hp per gallon of fuel per hour.
Fuel injected two strokes are very similar.
All of the tests produce figures that back up these figures.

Don't get hung up on fuel economy in terms of dollars, because as part of the total cost of boat ownership, a few dollars saved on fuel is insignificant.

[seamaid]

:) :) :)
Seamaid thanks reply post
Cheers Ged