Fuel economy - 140 Suzy

[suzygs1000]

Hi,

I recently fitted a Navman F215 fuel monitor to my boat.

I did a trip out to the reef, three weeks ago, and the gauge said that I had use 61 litres for a total trip of 131 k's.

At refill,the tank took 55 litres, which is what I assumed would have been about the usage based on previous trips.

I calibrated the F215 unit to match my actual usage.

I went to Trunk Reef on thursday.

Following info may be of some interest to members:

Boat ...plate alloy centre console
length, bow to transom.....5.8 m
length, bowsprit to swimplatform...6.1 m
estimated total weight (three aboard)...1500 kg's
motor....2007 140 Suzuki
prop...14x21 three blade standard Suzy ally
fuel...standard unleaded
weather.... 800mm chop outbound, calm on return.

Fuel usage.

The best I saw was about 15.6 lph , running at about 4000 rpms on the way home at about 40kph , dead flat sea.

The worst was while off the plane at around 3000 rpm, 20 kmh, 13 lph.

At cruise speed of 4200 rpm, 44 kmh, fuel usage was showing as 16.2 lph.

When the trip meter read 100 k's, on the way home, I hit the total usage button, which read 43.6 litres, => the boat was achieving 43.6 litres per 100 k's.

The total trip was 128 km's, for a total consumption of 53.1 litres.

This agrees pretty well with my historical usage for a trip to Trunk.

I recently fitted a 2000 x 2800 bimini top, and speed at 4000 rpm's increased by about 2 kms per hour, so fuel usage would have improved proportionaly, and I believe I am using about 2 to 3 litres per trip less with the bimini fitted.

From the above, it looks like on a good day, the boat will quite easily achieve 2.5 k's per litre, dropping to about 2.2 on a day with 800mm to a metre of chop.

Also, moving around the reef off the plane really chews the juice up!

I know exactly how much fuel I use at a refill, as I have the transparent reinforced fuel tank filler hose, and I have been filling it up until I see the fuel halfway up the filler hose.

Hope this is of interest to some members.

I know we often have discussions re the relative benefit of a four stroke over a normally aspirated two stroke, given the relative disparity in price of the two types.

My last boat was of similar length, but 200 kilos lighter then my current one.

It was fitted with a 2000 model Johnson 115hp Oceanpro, normally aspirated two stroke.

It used about 80 litres for the same trip.

With current fuel costs, this is about $32 more fuel, plus the two stroke oil.

Considering the relative resale values of the respective types of engines, I feel that the extra outlay for the four stroke is money well spent.


Hope this interests some members.

Dave.8-)

[ped cairns]

great motor, good info, but what about the fish

Ped

[Matt_F]

Round day trip to Trunk from Dungenes I used to use between 50 to 55L. I have a 4.5m tinny (alycraft tank) with a 40ph 2stk Yamaha tiller. No gauges so I just drive to the conditions. The motor is a bit on the smale side, but does the job. That just confirms that my next motor will be a 4stk.

[thylacene]

Great info thanks. Just a note, when looking at fuel consumption in litres per hour or litres per kilometer/100k's, the first number being lower is better.

When talking Miles per gallon or kilometres per litre, bigger is better for first number.

If your litres per hour were 13 off the plane and 15.6 on the plane then travelling speed needs to be taken into account. If you are doing 20KMH using 13L/Hr and 40KMH using 15.6L/HR then the motor is running more economically by .2L/HR @ 40KMH.

While I understand this, it is still difficult to wrap my head around given I grew up measuring fuel economy in MPG, the joys of getting old and being one of the in between generation. The move from measuring at MPG to measuring vehicle economy in L per 100Kms meant the maths equation had to be reversed.

If your L/per Hour went up with the Bimini fitted, then your economy decreased.

As a matter of interest, we did a 55Km trip and used 28 litres with a 5.6M hull and a 115HP EFI 4 Stroke Merc.

As we were stopped for part of it, I do not have per hour consumption, and speed varied depending on what we were up to at the time, but he maths for the distance covered on the trip are;

28 litres divided by 55 total kilometres = .509 L/Km multiplied by 100 = 50.9 L/100KM

Another example would be towing with your car. Around town we usually get 9L/100KM and highway we get 7.5L/100KM.

Hook the boat up and the car consumes 16L/100KM, effectively doubling the amount of fuel used. Good thing the car is leased as a package LOL.



Cheers

Thy