Monitoring Your Fuel Consumption - Fuel Flow Meters

[skip]

Perhaps one of the most important aspects when boating is trying to work out how much fuel you are using, so that you can estimate your max range, and be a bit more reassured than just looking at the fuel gauge.

One of the easiest things to do if you own an outboard is to fit a Digital Fuel Flow Gauge which consists of an inline flow sensor, and a long cable back to the digital instrument readout.

The flow sensor can be calibrated for supreme accuracy by passing around 10 gallons of fuel through it and then filling up your tank. You compare how much fuel you put in from the pump with how much fuel it reckoned you should have put in and adjust accordingly. Once set up it will maintain that accuracy all the way along.

I was doing some research this weekend, and for those who don't want to spend alot of money, I came across the <a href="http://www.northstarnav.com/en/Products/Instruments-Gauges/Fuel-210/" target="_blank">Northstar F210 Kit</a> The kit is designed for outboards and is a single gauge (if you have twin outboards you'll need two kits!), with a minimum measurable flow rate of 2.5 litres per hour up to a maximum of 130 litres per hour. The unit will display your current fuel flow rate, trip and total fuel consumption and low fuel alarm. In addition if you enter the total tank volume, it will show how much fuel is remaining.

I want to check with Northstar how the unit reacts when the engine is at very low RPM and fuel flow rate is below 2.5 litres per hour, as if it can't measure it, then it won't give an accurate fuel remaining figure etc. Incidentally this is not really an issue for two strokes as they idle at around 2.57 litres per hour!!!, it's only the 4-strokes and Direct Injection engines that can drop below 0.8 litres per hour.

The primary contenders for this kit are anyone running an outboard but especially those running a 2-stroke which are notorious for using alot of fuel. This kit will let you calculate your miles per gallon (mpg) or nautical miles per gallon (nmpg) providing you have a GPS onboard, and that in turn will then let you find the boat's sweet spot at cruise. Every boat is different, and it also varies on smaller boats depending on load and weight distribution, but a slight increase of a few hundred rpm might actually result in a huge consumption increase without you knowing.

It would also be useful to find your trolling sweet spot, maximum economy cruise (ie. the speed/rpm at which you get the best mpg) and the best fast cruise.

I've asked RLR for a price as they are the local reps for Northstar (who bought out Navman/Navico), however it is available online from Consumers Marine for $129.99, though I have seen it as low as $99.99

It shouldn't cost more than $30 to ship, add duty and VAT and it should work out to a landed cost of around Euro 125.00, a worthy investment.

As a side note, if anyone has a comptabile Lowrance head unit (GPS, Fishfinders etc) that has a NMEA2000 port on it, Lowrance make fuel flow meters and fuel level sensors which interface over NMEA2000 and can be displayed on the head unit without the need for a seprate gauge. Each sensor costs around $60.

[ciappinu]

Very informative Skip. Interesting to note is the difference in fuel consumption when on low rpms with 2 strokes. Infact, I calculate I need exactly 2.5litres of fuel every hour when I am trolling, and I only have a 3 year old 9.9hp. This is the last year I'll be using it, next year I'll be looking at an Etec if they release their new models, or a 20hp 4 stroke.

[skip]

The new ETEC 9.9hp etc should be very interesting, but I don't expect that they will be cheap though Evinrude will need to compete. As you may know, the Johnson 4 strokes are no longer being made in preparation for the smaller ETECs so they should be with us soon.

I think for trolling either a 4 stroke or Direct Injection engine is the way forward.

[skip]

Most of the modern 4 stroke or ECM controlled engines will display parameters like fuel flow etc via a Multifunction Digital Dash mounted gauge. Otherwise consider Lowrance's range of products that use NMEA 2000 and allow you to connect all sorts of accessories like fuel tank level meters, fuel flow etc.

[Granitu]

but wouldn't a 4 stroke suffer at low trolling speed, le's say ne has a 25-40hp etec outboard?

when i tried with a friend to troll with live bait with a 2 stroke at low speed we fouled the spark plugs 

[claudevella]

I have a 21ft bayliner with a 8hp 2 stroke and a 190hp 4 stroke (inboard). I always wondered which would be the mot economical to troll with ? - 8hp going nearly at WOT to get to trolling speed or the nearly idle 190hp which gives me the same trolling speed. Should i consider other variables - oil for 2 stroke, wear and tear etc? anyone with experience with similar engines?

[Moonwalker]

I am interested in such a meter too. I have Suzuki DF90 outboard. What type of meter fits with my outboard which is reliable and not too expensive. If I can use existing wiring its better.

[camkev]

http://shop.ebay.com/items/__Northstar-F210?_kw=Northstar&_kw=F210&_ckw=Kit&_trksid=p3286.m104.l1199

[skip]

Northstar as Kev pointed out or the Lowrance LMF-200 with the Suzuki interface cable but you'd better speak to Benri about hooking it all up!

[Moonwalker]

Since my motor is 4stroke and I leave it all day on, I may have a problem with the Northstar since its minimum is 2.5l/hr. I guess the Lawrence does not have that shortfall right?

[skip]

They all have some shortfall, I think the Lowrance reads down to around 1litre per hour

[Moonwalker]

I'm back again on this issue maybe this time I solve it.
I have the Furuno 585 that has a big enough display and which I dont really use it while cruising. It is NMEA 0183 though while my outboard is NMEA 2000. Now i came across a converter from NMEA 2000 to 183 - SimNet AT-10.
Anyone has tried this?